GB2220945A

GB2220945A - Resin-molded composition for coils

Info

Publication number: GB2220945A
Application number: GB8915945A
Authority: GB
Inventors: Hirofumi Kubo; Toshiyuki Fujimori; Tooru Koyama; Hirokazu Takasaki
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1988-07-22
Filing date: 1989-07-12
Publication date: 1990-01-24
Anticipated expiration: 2009-07-12
Also published as: JPH0232508A; GB8915945D0; GB2220945B; KR920005818B1; KR900002363A; JP2675086B2

Abstract

A resin-molded coil is made up of a winding, inner and outer circumferential insulation layers formed inside and outside said winding, and end insulation layers formed on the ends in the axial direction of said winding, wherein at least one of said inner and outer circumferential insulation layers, said end insulation layer, and the inside of said winding is a resin layer formed by filling a thermosetting resin composition under atmospheric pressure, followed by curing, said thermosetting resin composition being composed of a polyfunctional epoxy compound, filler, and a silane coupling agent and a titanate coupling agent in a specific ratio for the amount of said filler.

Description

RESIN-MOLDED COIL The present invention relates to a resin used to mold a coil and to a molded coil made from said resin. More particularly, the present invention relates to a thermosetting resin composition which meets all the requirements for good crack resistance, good heat resistance, and low viscosity, and to a resin-molded coil made from said thermosetting resi composition.

example of the resins used to mold coils is pro- cssed n Japanese Patent Laid-open No. 123457/1978. It as developed with the emphasis placed on the optimization of the particle size distributicn, maximum particle size, an average partIcle size of the inorganic filler.

However, it did not meet all the requirements for the reduction of viscosity, the improvement in heat resistance, and the improvement in crack resistance, because no consideration was given to the interfacial phenomenon between the organic matrix resin and the inorganic Japanese Patent Laid-open No. 113642/1986 suggests adding an inorganic filler to the organic matrix resin after direct treatment with a silane coupling agent or titanate coupling agent or both. The treatment is merely intended to render the filler hydrophobic. Therefore, this patent does not disclose the idea of improving wett ability of the filler by the resin, thereby meeting all the requirements for the reduction of viscosity, the improvement in heat resistance, and the improvement in crack resistance.

is is a conventional practice to incorporate in a resin a filler to increase the thermal conductivity and lower the linear thermal expansion coefficient, thereby to trove the cracks resistance. However, the incorporation Cf a filler increases the viscosity of the resin, making it di=zcult fcr the resin to infIltrate into the coil at the Lime of casting. To avoid this difficulty, vacuum a --s employed, as disclosed in Japanese Patent Laid open No. 138828/1980, or prcvision is made to prevent the resin from infiltrating into the coil, as disclosed in Japanese Patent Laid-open No. 121207/1982.

Japanese Patent Laid-open No. 224009/1987 discloses a method for increasing the amount of filler loading by reg ulating the particle size distribution of the filler and also for lowering the resin viscosity by incorporating the resin with a silane coupling agent.

Other related prior arts include Japanese Patent Publication Nos. 15553/1962 and 13814/1965. However, they do not disclose the idea of filling the resin under the atmo spheric pressure.

The above-mentioned prior art technologies are not nren.deå to meet all the requirements for improving the cracK resistance and heat resistance of the resin and low erin the viscosity of the resin. Therefore, they have the following disadvantages. (1) The incorporation of a are amount of filler into the resin for the improvement crack resistance increases the viscosity of the resin.

5 a resin needs vacuum casting for the coil impregna tion. Vacuum casting needs complex equipment and causes :oics in the ccil which bring about corona discharge in tre coil. (2) f the coil is not impregnated with the resin to prevent corona discharge, the coil has gets excessively hot on account of poor thermal conductivity.

According to the conventional practice, the filler incorporates 0.5-2% of silane coupling agent to reduce the viscosity of the resin. The incorporation of a siiae coupling agent lowers the viscosity considerably; ever, the effect does not increase in proportion to the amount of the silane coupling agent added, and the viscosity does not decrease below a certain limit. For example, the viscosity of a resin incorporating 60 vol% of filler will decrease from 30-50 poise to 20 poise if the resin incorporates a coupling agent in an amount of 3% (of the resin weight or 0.45% of the filler weight).

However, the viscosity never goes down to 10 poise or below. In other words, it is impossible for the prior art technology to lcwer the viscosity of 60% filled resin below 20 poise. Preferred embodiments of the present invention make @t possible to ameliorate one or more of the above-mentioned problems.

A peferrea emlDoaimenr may enable one to provide a thermosetting resin composition having superior heat resistance and crack resistance and a low vis comity, ant tc provide a resin-moided coil whic: can be end by casting under the atmospheric pressure and has superior heat resistance and corona characteristics.

Such embodiments employ a thermosetting resin composition containing a polyfunctional epoxy compound, filler, and coupling agent, said filler being incorporated with a silane coupling agent and =tanate coupling agent in a prescribed One class of embodiment of the present invention is a resin-molded coil made up of a winding, internal and external insulation layers formed inside and outside said winding, and end insulation layers formed on the ends in the axial direction of said winding, wherein at least one of said internal and external insulation layers, said end insulation layers, and the inside of said winding is made or said resin composition.

The thermosecting resin composition incorporating a large amount of filler may have a greatly reduced viscosity on account of the synergistic effect of the silane cou - -.a agent and titanate coupling agent incorporated thereir. The low-viscosity thermosetting resin composi tion permits casting under the atmospheric pressure for the easy production of resin-molded coils. The highly filled thermosetting resin composition may have a low linear --.e--a expansion coefficient close to that of the ccil con c' -; therefore, the resin composition has improved crack resistance. The silane coupling agent and titanate coupling agent incorporated into the filler in a certain ratio prevent the decrease of the glass transition point cf the resin, thereby increasing the heat resistance of the resin.

Some embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which Fig. l is a perspective view partly in section showing the structure of the resin-molded coil in Example 1 of the present invention.

Fig. 2 is a perspective view showing the external appearance of the resin-molded coil in Example 1 of the present invention.

tic. 3 is a sectional view showing the winding of the resin-molded coil.

Fig. 4 is a partly enlarged detail of Fig. 3.

Figs. 5 te 7 illustrate the method of producing the resin-molded coil In Example 1 of the present invention.

5 s is = side view showing the coil, with the core r..ounte on the winder the winding, and the internal and external insulation layers attached.

Fig. 6 is a side view showing the winding impregnated with the resin, with the core dismounted from the winder.

-i . 7 is a side view showing the winding, with the core removed, which has undergone curing.

Fig. 8 -is a graph showing the change of the viscosity caused by the incorporation of the coupling agent.

Fig. 9 is a graph showing the change of the glass transition point caused by the incorporation of the titarate coupling agent.

Fig. 10 is a graph showing the relation between the degree of vacuum and the corona starting voltage.

Fig. 11 is a table which compares the characteristic properties of the resin composition in the example of the present invention with those of the conventional resin composition.

Fig. 12 is a side view partly in section showing the resin-molded coil in Example 2 of the present invention.

Fig. 13 is a side view partly in section showing the resi-molded coil in Example 3 of the present invention.

Fig. 14 is a side view partly in section showing the resin-molded coil in Example 4 of the present invention.

i. 15 is a perspective view partly in section snowing the resin-molded coil in Example 4 of the present invention.

Fig. 16 is a side view partly in section showing the resn-molded co-: in Example 5 of the present invention.

Fig. 17 is a perspective view partly in section showing the resin-molded coil in Example 5 of the present invention.

Figs. 18 to 22 are side views partly in section showing the resin-molded coils in Example 6 to 10, respectively.

Figs. 23 to 30 are side views partly in section showing the resin-molded coils in Example 11 to 18, respectively.

Fig. 31 is a sectional view showing the resin-molded.

coil in Example 19 of the present invention.

Fig. 32 is a perspective view showing the resinmolded coil in Example 19 of the present invention.

Fig. 33 is sectional view showing the resin-molded coil in Example 20 of the present invention Fig. 34 is a perspective view showing the external shape of the resin-molded coil in Example 21 of the present invention.

Fig. 35 is a sectional view through section B-B' of 5. 34.

Fig. 36 is a sectional view through section C-C' of ig. 34.

Fig. 37 is a sectional vies through section D-D' of .Fig. 34.

Fig. 38 is a perspective view showing the resinmolded coil used as a transformer.

Fig. 39 is a perspective view showing the external shape of the resin-molded coil in Example 22 of the present invention.

Fig. 40 is a perspective view showing the resin ~molded coil used as a transformer.

Fig. 41 is a perspective view showing the external shape of the resin-molded coil in Example 23 of the present invention.

Fig. 42 is a perspective view showing how the coil is placed in a casting mold in Example 23 of the present invention.

Fig. 43 is a sectional view showing the completion of the casting of the low-viscosity resin liquid.

The invention will be described in more detaii with reference to the following examples.

Example 1 This example will be explainec with reference to Figs. 1 11. Fig. 1 is a perspective view partly in section showing rhe S;vucture of the resin-moldeo coil in this example. The resin-moled coil i is maae up of the internal insulation layer (inner circumference insulation layer) 5 moloed of prepreg insulation material Sa, the external insulation layer (outer circumference insulation layer) 6 molded of prepreg insulating material 6a, and the resin-impregnated winding 4 which has been heat-cured after casting.

The resin-molded coil in this example is produced in the following manner. The winding 4 is formed by winding the conductor 4a and the inter layer insulating material 4b 0lternately on the core 7 as shown in Fig. 3, usln the winder 8 as shown In Fig. . The winding 4 is formed in close contact with the flange 7a which prevents the leakage of the resin. After the completion of the winding 4, the prepreg insulating material 6a is wound around the winding 4, with one edge thereof in close contact with the flange 7a. The winding 4 is dried and the prepreg insulating materials 5a and 6a are cured.The resin composition 9 is cast under the atmospheric pressure into the space surrounded by the prepreg insulating materials 5a and 6a and the interstice in the winding 4, with the flange 7a positioned down, as shown in Fig. 6. The resin composition is prepared by filling a polyfunctional epoxy compound with a filler and then incorporating the filled compound with a silane coupling agent and a titanate cou pliny agent at a prescribed ratio, so that it has a low viscosity and good heat resistance and crack resistance.

After curing, the core 7 is removed, and there is obtained the resin-molded coil 1 having a cross-section as shown in Fig. 7. By using the core 7 havIng a rectangular crosssection in the direction perpendicular to the axis of the core 7, it is possible to produce the rectangular coil as shown in Fig. 2.

For the complete infiltration into the molded coil, the resin should have a viscosity as low as 10 poise (at 100C at the time of casting). The resin viscosity can be lowered when the amount of filler is reduced. However, this causes the following problems.

(a) Decreased thermal conductivity.

(b) Increased linear thermal expansion coefficient, which leads to lower crack resistance.

(c) Increased production cost.

The infiltration of the resin composition can be improved if casting is carried out in a vacuum. However, tZ:i5 causes voids in the cast resin. The voids induce corona discharge. (The higher the degree of vacuum, the ower the corona starting voltage, as shown in Fig. 10.) Therefore, it is desirable that casting be carried out completely under the atmospheric pressure. To achieve - objective, it is essential to lower the resin viscos - ,. The resin viscosity can be lowered by the aid of ocu- -. agents.

curling agents include silane coupling agents and titanate coupling agents, with the former being in common use. The decrease of resin viscosity which is achieved by the aid of a silane coupling agent is limited as shown in Fig. . According to the common practice, a silane cou jing agent is added in an amount of 0.5-2 wt% of the filler to lower the resin viscosity. The incorporation cf a silane coupling agent lowers the resin viscosity considerably as shown in Fig. 8. The resin viscosity goes down in proportion to the amount of silane coupling agent added; however, the resin viscosity levels off when the amount of silane coupling agent exceeds a certain value.

For example, the viscosity of a resin incorporated with 60 vol of filler will decrease from 30-50 poise to 20 poise if the resin is incorporated with a coupling agent in an amount of 3t (of the resin weight or 0.45% of the filler weight) . Therefore, it is desirable that the amount of the silane coupling agent be about 0.3-1.5% of the filler -..e ch. However, the viscosity never goes down to 10 poise or below. In other words, it is impossible fcr the siiane coupling agent alone to lower the viscosity of 60 ijed resin below 20 poise.

On the other hand, if the amount of coupling agent is increased, the resulting resin composition decreases in heat resistance and glass transition point (Tg). This hoids true particularly of titanate coupling agents, as shown in Fig. 9.

It was found that a silane coupling agent and a tit an nate coupling agent remarkably lower the resin viscosity when used in combination with each other. Fig. 8 shows the viscosities of three resins, each incorporated with t. 5 t (of the filler) of silane coupling agent and O.075 wt%, 0.15 wt%, and 0.6 wt% (of the filler or 0.5 wt%, 1 watt and 4 wt% of the resin) of titanate coupling agent. The effect of viscosity reduction levels off when the amount of titanate coupling agent is increased more than 0.15 wt%. Rather, the increased amount of titanate coupling agent lowers the Tg and also lowers the heat resistance to a great extent.Therefore, it is desirable that the amount of titanate coupling agent be about 0.05-0.3%. The foregoing is summarized in Fig. 11. Resin represents an embodiment in the present invention.

ecl 3 represents a conventional resin incorporated with ne silane coupling agent. It should be noted that it has a viscosity as high as 20 poise and a Tg of 120 C. Resin C represents a resin incorporated with a titanate coupling agent alone. It should be noted that it has a low viscos --y z- 9 poise, but it also has a low Tg.

According to the present invention, the resIn viscos- :-i s greatl reduce, without a substantial decrease in g, by incorporating the resin with a silane coupling agent in combination with a small amount of titanate coupling agent. The resin composition in this example has a Tg of ;35 C, and hence it can be used as an F-class insulatin material.

The thermosetting resin composition used in this example is composed of an epoxy compound (which is glycidyl ether obtained by the reaction of bisphenol-A and bisphenol-F with epichlorohydrin), a filler (which is crystalline silica), a hardener (which is anhydrous hexahydrophthalic acid), a cure accelerator (which is 2-ethyl-4-methylimidazole), a silane coupling agent (which is y-glycidoxypropyltrimethoxysilane), and a titanate coucling agent (which is isopropyl trllsostearoyl titanate).

The filler used in this example is one which has the maximum particle diameter smaller than 80 Fm and also has such a particle size distribution that the slope (n) of the RRS particle size distribution curve is smaller than G.9, as described in Japanese Patent Laid-open No.

224009/1987. This specific filler was used to make the resin composition have the linear thermal expansion coef -ic enr close to that of the winding conductor when the loading 5 S as high as 60 vol%. The resin composition has a linear thermal expansion coefficient of 2.4 x 10-j (K), which is close to 2.3 x 10-5 (K-i) of aluminum.

According to this example, the resin composition can be cast under the atmospheric pressure on account of its low viscosity. It infiltrates into the interstice in the winding and hence greatly improves the heat dissIpation properties of the coil. As the result, the resin-molded coil can be made small and the production of inexpensive molded transformers becomes possible.

This example has an additional advantage attributable to casting under the atmospheric pressure. Even though voids 9a occur in the winding as shown in Fig. 4, the pressure in the voids 9a is almost equal to the atmo spnero pressure; therefore, the corona starting voltage is .igh as shown in Fig. 10 and the voids 9a do not permit zrsne to take place even in the case of electric field concentration.

Example 2 ris examle will be explained with reference to Fig.

12. The resin-molded coil 20 is made up of the internal insulation layer 5 formed from the prepreg insulating material 5a, the external insulation layer 6 formed fro - epreg insulating material 6a, and the lower part by filling a high-viscosity putty-like resin 14.

The low viscosity liquid resin 9 is cast into the winding fro the top, followed by heat-curing.

The resin-molded coil in this example is produced by mounting the core 7 on the winder 8, winding the prepreg insulating material 5a, and winding the conductors of the windings 4, as shown in Fig. 5.

In this example, too, the winding 4 is formed by winding the conductor 4a and the interlayer insulating material 4b alternately. After the completion of the winding 4, the prepreg insulating material 6a is wound thereon. Subsequently, one end of the winding is filled with a high-viscosity putty-like resin 14. The winding 4 is dried and the prepreg insulating materials 5a and 6a and the putty-like resin 14 are cured by heating. The core 7 is removed, and the coil is placed, with the filled end down. The low-viscosity liquid resin 9 is cast into the winding 4 from the top under the atmospheric pressure.

ton heat-curing, there is obtained the resin-molded coil 20. The low-viscosity liquid resin 9 contains a silane coup ing agent and a titanate coupling agent In a specific ratio for the filler, and has a low viscosity and good eat resistance and crack resistance.

According to this example, the core 7 needs no ~angel therefcre, the resin-molded coil is simple in structure and low in production cost. In addition, the method in this example can be used regardless of the thickness of the winding 4 in its radial direction. Con sequently, it is suitable for the production of varied types each in small quantities.

Example 3 Thfs example will be explained with reference to Fig.

13. The resin-molded coil in this example is different from those mentioned above in that the resin layer formed by curing the low-viscosity liquid resin 9 is present only in the winding 4, as shown in Fig. 13.

The resin-molded coil 30 is made up of the internal insulation layer 5 formed form the cured prepreg 5a, the external insulation layer 6 formed from the cured prepreg 6a, and the end insulation layers 10 at the ends in the axial direction of the winding 4. The end insulation layers 0 are formed from the cured putty-like resin 14.

the winding 4 is made up of the conductor and interlayer tauter ich are wound alternately. In the winding is the resin layer 9 which is formed by casing the low-viscosity cuid resin 9, followed by curing. The resin-moldec cci n nis example is produced in the same manner as in =xar.le 2, except that the low-viscosity liquid resin 9 is cast into the winding 4 under the atmospheric pressure up to the upper end of the winding 9, and the upper end insulation layer 10 is formed by filling the puttyl-like resin 14. Upon heat-curing, there is obtained the resin-molded zsil 30.

Example 4 This example will be explained with reference to Figs. 14 and 15. The resin-molded coil 32 in this example is made up of the resin layer 9 formed in the winding 4 from the low-viscosity-liquid resin 9, the external insulation layer 6 formed from the prepreg 6a, the internal insulation layer 5 formed from the prepreg Sa, the resin layer 9 formed from the low-viscosity liquid resin 9, and the end insulation layers 10 formed from the putty-like resin 14.

The resin-molded coil in th s example has the spacers 32a interposed between the internal prepreg 5a and the winding 4. The low-viscosity liquid resin 9 is cast Into the space between the prepreg 5 and the winding 4 so that the resin layer cf the low-viscosity liquid resin 9 is formed inside the winding 4. The spacers 32a should pre -erably be of the same material as the resin to be cast.

n this example, the spacers 32a are formed by curing the low-viscosity liquid resin 9.

The resin-molded coil 32 in this example is produced by mounting the core 7 (not shown) cn the winder 8 (not shown), winding the internal prepreg 5a on the core 7, and winding the conductor of the winding 4 thereon, with the spacers 32a interposed. The winding 4 is formed by winding te conductor 4 and the interlayer insulating material 4b alternately. The spacers 32a should preferably be shorter than the prepreg 5a in its axial direction and longer than the winding 4 in its axial direction.

Fig. 15 shows the resin-molded coil in which the spacers 32a are as long as the prepreg 5a in its axial direction.

softer the completion of the winding 4, the prepreg 6a is wor.d around the winding 4 so as to form the external insulation layer 6. Subsequently, one end is filled with the p-tty-like resin 14. The assembly together with the cr --e heat-cured so that the winding 4 is dried, and the prepregs 5a and 6a and the putty-like resin 14 are ore. The ccre 7 is removed, and the coil is placed, wlth tre end filled with the putty-like resin 14 down.

The low-viscosity liquid resin 9 is cast under the atmospheric pressure into the winding 4 and the space formed by the spacers 32a between the prepreg 5a and the winding 4. The upper enc is filled with the putty-like resin 14.

Upon heat-curing, there is obtained the resin-molded coi 32.

The resin-molded coil 32 in this example has an increased thickness of the internal insulation layer, so that it is possible to increase the insulation strength between the winding 4 and the iron core inserted into the space formed after the removal of tre core 7.

Example 5 This example will be explained with reference to Figs. 16 and 17. The resin-molded coil 34 in this example is made up of the winding 4, the resin layer 9 formed inside the winding 4 from the low-viscosity liquid resin 9, the internal insulation layer 5 formed from the prepreg Sa, the external insulation layer 6 formed from the prepreg 6a, the resin layer 9 formed from the lowviscosity liquid resin 9, and the end insulation layers 10 formed from the putty-like resin 14.

The resin-molded coil in this example has the spacers 34a interposed between the external prepreg 6a and the winding 4. The low-viscosity liquid resin 9 is cast into the space between the prepreg 6a and the winding 4 so that the resin layer cf the low-viscosity liquid resin 9 is formed outside the winding 4. The spacers 34 should preferably be of the same material as the resin to be cast.

In this example, the spacers 34a are formed by curing the low-viscosity liquid resin 9.

The resin-molded coil 34 in this example is produced by mounting the core 7 (not shown) cn the winder 8 (not shown), winding the internal prepreg 5a on the core 7, and winding the conductor of the winding 4 thereon. The winding 4 is formed by winding the conductor 4a and the interlayer Insulating material 4b alternately. After the completion of the winding 4, the prepreg 6a is wound outside the winding 4, with the spacers 34a interposed.

The spacers 34a should preferably be shorter than the prepreg 6a in its axial direction and longer than the winding 4 in its axial direction. Fig. 17 shows the resin-molded coil in which the spacers 34a are as long as the winding 4 in its axial direction.

Subsequently, one end is filled with the putty-like resin 14. The assembly together with the core are heatcured so that the winding 4 is dried, and the prepregs 5s and 6a and the putty-like resin 14 are cured. The core 7 is removed, and the coil is placed, with the end filled tit the putty-like resin 14 down. The low-viscosity livid resin 9 is cast under the atmospheric pressure into the wir.ding- 4 and the space formed by the spacers 34a between the prepreg 6a and the winding 4. The upper end Is filed wit the putty-like resin 14. Upon heat-curing, there is obtained the resin-molded coil 34.

The resin-moided coil 34 in this example has an increased thickness of the external insulation layer, so that it is possible to increase the insulation strength of the outside of the coil. Therefore, the resin-molded coil has good insulation properties and safety.

Example 6 This example will be explained with reference to Fig.

18. The resin-molded coil 36 in this example is made up of the winding 4, the resin layer 9 formed inside the winding 4 from the low-viscosity liquid resin 9, the internal insulation layer 5 formed from the prepreg Sa and the resin layer of the low-viscosity liquid resin 9, the external insulation layer 6 formed from the prepreg 6a, the resin layer 9 formed from the low-viscosity liquid resin 9, and the end insulation layers la formed from the putty-like resIn 14.

The resin-molded coil in this example has the spacers (not shown) interposed between tthe internal prepreg 5a and the winding and also between the external prepreg 6a and the winding 4. The low-viscosity liquid resin 9 is cast into the space between the prepregs Sa and 6a and the winding 4.

The resin-moided coil 36 in this example is produced by combining the methods for producing the resin-molded coils in Examples 4 and 5.

The resin-molded coil 36 in this example is produced by mounting the core 7 (not shown) on the winder 8 (not shown), winding the internal prepreg 5a on the core 7, and winding the conductor of the winding 4 thereon, with the spacers (not shown) Interposed. The winding Z is formed by winding the conductor 4a and the interlayer insulating material 4b alternately. After the completion of the winding 4, the prepreg 6a is wound outside the winding 4, with the spacers (not shown) interposed.

Subsequently, one end is filled with the putty-like resin 14. The assembly together with the core are heatcured so that the winding 4 is dried, and the prepregs 5a and 6a and the putty-like resin 14 are cured. The core 7 is removed, and the coil is placed, with the end filled t r. te putty-like resin 14 down. The low-viscosity i o resin 9 is cast under the atmospheric pressure into the winding 4 and the space formed by the spacers between the prepregs 5a and 6a and the winding 4. The upper end ed fills with the putty-like resin 14. Upon heat-curing, tn ere is obtained the resin-molded coil 36.

According to this example, it is possible to improve the insulation strength and mechanical strength of the internal and external layers on the coil, and hence it is possible to produce a resin-molded coil having outstanding insulation properties and reliability.

Examples 7 to 9 These examples will be explained with reference to igs. 19 to 21, respectively. These examples are the mod i=icatlons of Examples 4, 5, and 6, respectively. The modification was made by forming the upper end insulation layer from the low-viscosity liquid resin 9 in place of the putty-like resin 14.

The resin-molded coils in these examples are produced in the same manner as in Examples 4 to 6, except that the step of filling the upper end with the putty-like resin.

In these examples, the low-viscosity liquid resin 9, in place of the putty-like resin 14, is cast into the winding 4 under the atmospheric pressure until the upper end of the winding 4 is covered as thick as necessary. Upon heat-curing, there are obtained the resin-molded coils 38, 0, and 42. According to these examples, it is not necessary to fill the upper end with the putty-like resin.

This leads to the reduction of working steps.

Example 10 This example will be explained with reference to Fig.

Tis example is a modification of Example 9. The r..odification was made by forming both the upper and lower ends from the low-viscosity liquid resin 9. The resinmolded coil in this example is produced by combining the methods in Examples 1 and 6.

The resin-molded coil 44 in this example is produced by mounting the core 7 (not shown) having the resin shielding flange 7a on the winder 8 (not shown), winding tne internal prepreg 5a on the ccre 7, with one edge thereof kept in close contact with the flange 7a, and winding the conductor of the winding 4 thereon, with the spacers (not shown) interposed. The winding 4 is formed by winding the conductor 4a and the interlayer insulating material 4b alternately. After the completion of the winding 4, the prepreg 6a is wound outside the winding 4, :1 th the spacers (not shown) interposed. The prepreg 6a is wound, with one edge thereof kept in close contact with the flange 7a.After the prepreg 6a has been wound, the is a 4 is dried and the prepregs 5a and 6a are cured.

bsequently, with the flange 7a positioned down, the lowviscosity liquid resin 9 is cast under the atmospheric pressure into the space surrounded by the prepregs 5a and a, the space formed by the spacers between the winding 4 and the prepregs 5a and 6a, and the interstice in the winding 4. After curing, the core 7 is removed, and there -s ^^aineå the resin-molded cOil 44. According to this example, the internal insulation layer 5 is formed from the prepreg Sa and the resin layer 9, and the external layer 6 is formed from the prepreg 6a and the resin layer 9.

The resin-molded coils in Example 7 to 10 have the end surfaces and at least either of the internal layer or external layer on the winding 4 which are formed from the low-viscosity liquid resin 9. Therefore, they have improved weather resistance on account of the air-tight, waterresistant resin layer formed on the winding.

The resin-molded coils in Examples 7 to 9 have one of the insulation layer formed from the putty-like resin 14.

However, they may have both of the end insulation layers formed from the low-viscosity liquid resin 9 as in Example 10, so that they have further improved weather resistance.

Example 11 This example will be explained with reference to Fig.

23. The resin-molded coil in this example has the shielding l--vers (obstructing layers) 16 at the upper and lower ends of tne winding 4 which. prevent the infleration of the lowviscosity liquid resin 9, and also has the air layer 18 in the winding 4.

The resin-moided coil in tis example has the internal insulation layer 5 formed from the prepreg 5 and the external insulation layer 6 formed from the prepreg 6a, and the shielding layers 16 formed from the putty-like resin 14 at both ends of the winding 4. The low-viscosity liquid resin 9 is cast into the space surrounded by the shielding layers 16 and the prepreg 5a and 6a.

The resin-molded coil 59 in this example is produced in the same manner as in Example 2 up to the steps of winding the prepreg 6a around the external insulation layer. After the prepreg 6a has been wound, both ends of the winding 4 are filled with the putty-like resin 14 as thick as necessary to prevent the infiltration of the lowviscosity liquid resin. This procedure is performed under the atmospheric pressure, so that the air layer 18 in the winding 4 has a pressure equal to the atmospheric pressure.

"'he internal and external insulation layers 5 and 6 and the shielding layer 16 are formed by heat-curing the prepregs 5a and 6a and the putty-like resin 14. Subse quently, the core 7 is removed, and the coil is posi ion e , with one end thereof upward. The low-viscosity cuic resin 9 is cast into the space surrounded by the prepregs 5a and 6a and the shielding layer 16, followed by curing. Then, the coil is inverted, and the low-viscosity liquid resin 9 is cast into the space surrounded by the prepregs Sa and 6a and the shielding layer 16 at the other end, ollowed by curing. Thus, there is obtained the resin-molded coil 50.

The resin-molded coil 50 in this example has an advantage of being light in weight on account of the air layer in the winding 4.

Examples 12 to 14 These examples will be explained with reference to iis. 2 to 26, respectively. The resin-molded coils in these examples are the modifications of those in Example 4 to 6. The modification is made by replacing the resin layer 9 in the winding 9 with the air layer 18.

The resin-molded coils in these examples have an advantage of being light in weight on account of the air layer in the winding. In addition, the internal and external layers of the low-viscosity liquid resin improve the insulation strength. According to these examples, the shielding layer 17 provided inside or outside of the winding 4 is formed from the interlayer insulating material 4b'of the winding 4. It is not necessary to form the shielding layer on the upper and lower ends of the winding because they are filled with the putty-like resin 14.

The resin-molded coils in these examples are produced ifl fle same manner as in Examples 4 to 6, respectively, except that the low-viscosity liquid resin is nct cast Into the winding 4.

xamples 15 to 17 These examples will be explained with reference to Figs. 27 to 29. These examples are the modifications of Examples 12 to 14, respectively. According to these examales, the upper end insulation layer is also formed from the low-viscosity liquid resin 9. The resin-molded coils in these examples have the shielding layer 16 formed on ne upper end of the winding w from the putty-like resin 14. The shielding layer 16 prevents the low-viscosity liquid resin 9 from infiltrating into the winding 4. On the inside or outside of the winding 4, the interlayer insulating material 4b which has been wound functions as the shielding layer 17.The resin-molded coils 58, 60, and 62 in these examples are produced in the same manner as in Example 4 to 6, respectively, up to the step of forming the lower insulation layer 10 from the putty-like resin 14 by heat-curing. After this step, the upper part o the induing 4 is filled with the putty-like resin 14 as thick as necessary to form the shielding layer 16 which prevents the infiltration of the low-viscosity liquid resin 9. Subsequently, the low-viscosity liquid resin 9 is C25~ into the space formed by the spacers between the winding 4 and the internal prepreg 5a or the external prepreg 6a.Then, the low-viscosity liquid resin 9 is cast nto the space surrounded by the prepregs 5a and 6a atcve the shielding layer 16. The low-viscosity liquid resin 9 is cast until it reaches the edge of the prepregs Sa and 6a. The low-viscosity liquid resin 9 does not infiltrate into the winding 4 because the wound interlayer insulating material 4b functions as the shielding layer 17 on the inside or outside of the winding 4. This procedure is performed under the atmospheric pressure so that the inside of the winding 4 has the air layer which is balanced with the atmospheric pressure.Finally, the lowviscosity liquid resin 9 is heat-cured, so that the resin layer of the low-viscosity liquid resin 9 is formed on the upper end and the inside or outside of the winding 4. The thus formed resin-molded coils have improved weather resistance and heat dissipation.

Example 18 This example will be explained with reference to Fig.

30. This example is a modification of Example 17.

According to this example, the shielding layer 16 is formed from the putty-like resin 14 on the upper and lower ends of the winding 4, and the resin layer is formed from the low-viscosity liquid resin 9 on the upper and lower ends of the resin-molded coil. The resin-molded coil in this example is produced in the same manner as in Example c' up to the step of winding the prepreg 6a, with the spacers interposed around the outside of the winding 4.

According to this example, the upper and lower ends of the winding 4 are filled with the putty-like resin 14 as thick as necessary to prevent the infiltration of the lowviscosity liquid resin. With the lower end of the resinmolded coil 64 closed, the low-viscosity liquid resin 9 is cast through the upper end. The lower end may be closed --y providing the core 7 with the detachable flange 7a in close contact with the lower end of the internal and external prepregs 5a and 6a prior to the casting of the low-viscosity liquid resin 9. The cast low-viscosity liquid resin 9 flows downward through the space formed by the spacers between the inside of the winding 4 and the prepreg 5a and between the outside of the winding 4 and the prepreg 6a.Then, it fills the space formed by the spacers between the flange 7a and the prepregs 5a and 6a and between the inside and outside of the winding 4 and the prepregs 5a and 6a. Finally, it fills the space surrounded by the shielding layer 16 at the upper end of the winding 4 and the internal and external prepregs Sa and 6a. The low-viscosity liquid resin 9 is filled up to the same eIght of the edge of the internal and external prepreys 5a and 6a.Upon heat-curing of the low-viscosity icui a resin 9, there is obtained the resin-molded coil -'. The rein-molded coil in th s example has improved weather resistance and heat dissipation because the resin layer of the low-viscosity liquid resin 9 is formed on the entire surface of the winding 4.

Incidentally, in the foregoing examples, the end having the lead wires 2 and 3 is designated as the upper side. However, the end opposite to the end having the lead wires 2 and 3 may also be designated as the upper side.

Example 19 This example will be explained with reference to Figs. 31 and 32. In this example, the invention applied to the cast-type resin-molded coil 70. According to this example, the winding 4 is disposed in the casting mold (not shown) and the low-viscosity liquid resin 9 is cast into the mold through the inlet (not shown), so that the low-viscosity liquid resin 9 forms the end insulation layer 78, the internal insulation layer 74, and the external insulation layer 76, and infiltrates into the winding 4. Upon heat-curing, there is obtained the resin-molded coil 70 having tap changing terminals 71 as shown in Fig.

32. In this example, the low-viscosity liquid resin 9 can be cast under the atmospheric pressure on account of its low viscosity. Therefore, it is possible to eliminate the vacuum equipment and reduce the equipment cost to a great extent. Incidentally, Fig. 31 is a sectional view through section A-A' of Fig. 32. It should be noted that in this example, the resin 9 is filled also into the winding 4 as shown in Fig. 31.

Example 20 This example will be explained with reference to Fig.

33. The resin-molded coil in this example differs from that in Example 19 in that the winding 4 is not impregnated with the resin 9. The resin-molded coil 72 according to this example has an external appearance as shown in Fig. 32. It is constructed such that the upper and lower ends in the axial direction of the winding 4 are previously filled with the putty-like resin 14 to form the shielding layer which prevents the resin 9 from infiltrat ng into the winding 4. The inside and outside of the winding 4 are provided with the shielding layer 17 of the wound interlayer insulating material 4. The filling of the ut e r and lower ends of the winding 4 with the putty ike resin 14 and the casting of the resin 9 into the astino mold (nct shown) are accomplished under the atmo seric pressure, so that the air layer 18 having the atmosheric pressure is formed in the winding 4. The resin-molded coil 72 in this example is light in weight because the space in the winding 4 is left unfilled. The example is suitable for the resin-molded coil of small capacity with less heat generation.

The resin-molded coil in this example is produced in the same manner as in Example 19, except that both ends of the winding 4 are provided with the shielding layer 16 before the winding 4 is disposed in the casting mold.

Example 21 This example will be explained with reference to Figs. 34 to 38. The resin-molded coil in this example is constructed such that the terminal on the surface of the external insulation layer is surrounded by a rib to extend the insulation distance. The formation of the rib is possible on account of the high fluidity of the low-viscosity liquid resin 9. In Fig. 34, there are shown the terminal 81 for the start of the winding, the terminal 82 for the end of the winding, and the terminal 83 for tap changing.

Figs. 35 to 37 are respective sectional views through sections B-3', C-', and D-D' in Fig. 34. The terminals 81 and 82 are surrounded by the ribs 64 and 85, respectively.

The height of the ribs 84 and 85 projecting from the surface of the resin-molded coil is smaller than that of the terminals 6 and 82, so that the ribs do not interfere with the connection of the lead wire. This holds true of the tap changing terminal 83 and the rib 86. The resinmolded coil 80 has the internal insulation layer 80a, the external insulation layer 80b, and the end insulation layer 80c formed from the low-visccsity liquid resin 9.

Having a good fluidity, the low-viscosity liquid resin 9 fills completely the casting mold having a complex configuration, forming the ribs as in this example. The winding 4 may or may not be impregnated with the low-viscosity liquid resin 9. The resin-molded coil 80 in this example is produced in the same manner as Example 19 or Example 20. Fig. 38 shows the resin-molded coil 80 in this example which is used as a single-phase transformer. The, resin-molded coil 80 is slipped on the iron core 87. To the terminal 81 is attached the terminal 88 for the primary source. To the terminal 82 is attached the con nectlng bar 89. To the tap terminal 83 is attached the tap connecting bar 90. The secondary terminals 91 are connected for the single-phase three-wire system.

Example 22 This example will be explained with reference to igs. 39 and 40. The resin-molded coil in this example has radiation ribs 92a on the external insulation layer 92c which can be formed by taking advantage of the good fluidity and thermal conductivity of the low-viscosity liquid resin 9. The resin-molded coil 92 in this example as the internal insulation layer 92b, the external insulation layer 92c, and the end insulation layer 92d which are formed from the low-viscosity liquid resin 9. The radiation ribs 92 are formed by casting, followed by curing, the low-viscosity resin 9 into a casting mold (not shown) having the configuration of the radiation ribs 92a.

The resin-molded coil in this example is produced in the same anner as n Example 19 or 20.

Fig. 40 shows the resin-molded coil 92 of this example which is used as a transformer of single-phase three-wire system. The resin-molded coil in this example has the ribs 92a only on the front side and rear side, so that a plurality of the coils can be arranged side by side without the possibility that the ribs interfere with one another or the ventilation is impeded by the ribs.

In the above-mentioned examples, the resin composition is incorporated with both a silane coupling agent and a titanate coupling agent, so that the filler has improved wettability by the resin and the molecules of the resin are arranged compact. Therefore, the resin-molded coil has such good air-tightness and water- and moistureproofness that it can be used outdocr.

Example 23 This example will be explained with reference to Figs. 41 to 43. The resin-molded coil in this example is designed for linear motors. The resin-molded coil in this example has the winding 102 impregnated with the lowviscosity liquid resin 9 and the internal insulation layer 107, the external insulation layer 108, and the end insulation layer 110 formed around the winding 102 from the low-viscosity liquid resin 9.

The resin-molded coil in this example is produced by disposing the winding 102 in the casing mold 106, with the spacers 104 inserted beneath, and casting the lowviscosity liquid resin 9. The casting mold 106 has the fluted bottom 106a so that the ribs 112 are formed on the resin-molded coil. The ribs 112 function as radiation ribs and reinforcing ribs. The resin-molded coil in this example has improved weather resistance and heat radi aton.

The resin-molded coils in the foregoing examples have advantages of cost reduction and Improved heat radiation.

The cost reduction is attributable to the fact that the resin can be incorporated with a much larger amount of tiller tan the conventional resin. The improved heat racation is attributable to the high heat conductivity of te filler. Owing to the improved heat radiation, the resin-olded coil of the present invention can be reduced ifl size by about 20% as compared with the conventional one. In addition, the resin-molded coil of the present invention is lighter than the conventional one and can be produced with a lower material cost and equipment invest ment than the conventional one.

The present invention provides a small-sized lightweight resin-molded coil for high current density having improved heat resistance and crack resistance.

The present invention provides a thermosetting resin composition having a low viscosity and good heat resistance and crack resistance.

The thermosetting resin composition embodying the present invention may have such a low viscosity that it can be cast under atmospheric pressure. This makes the casting operation easy and obviates the complex vacuum casting equipment. Therefore, the present invention permits the great reduction of equipment cost.

Claims

CLAIMS:

1. A resin-molded coil having a winding, inner and outer circumferential insulation layers formed inside and outside said winding, and end insulation layers formed on the ends in the axial direction of said winding, comprising a resin layer disposed in at least one of said inner and outer circumferential insulation layers, said end insulation layers, and the inside of said winding, said resin layer being formed by filling a thermosetting resin composition under atmospheric pressure, followed by curing, said thermosetting resin composition being composed of a polyfunctional epoxy compound, filler, and a silane coupling agent and titanate coupling agent in a specific ratio for the amount of said filler.

2. A resin-molded coil having a winding, inner and outer circumferential insulation layers formed inside and outside said winding, and end insulation layers formed on the ends in the axial direction of said winding, comprising a resin layer disposed in at least one of said inner and outer circumferential insulation layers and said end insulation layers; said resin layer being formed by filling a thermosetting resin composition under atmospheric pressure, followed by curing, said thermosetting resin composition being composed of a polyfunctional epoxy compound, filler, and a silane coupling agent and titanate coupling agent in a specific ratio for the amount of said filler, there being an obstructing layer disposed on the surface of said winding facing to said resin layer, so as to prevent said resin from infiltrating into said winding.

3. A resin-molded coil according to claim 1, wherein said resin layer is formed inside said winding.

4. A resin-molded coil according to claim 3, wherein said inner circumferential insulation layer and outer circumferential insulation layer are formed from a heat-cured prepreg and at least either of said end insulation layers being said resin layer.

5. A resin-molded coil according to claim 4, wherein one of said end insulation layer is said resin layer and the other of said insulation layer is formed from a putty-like resin.

6. A resin-molded coil according to claim 3, wherein said inner circumferential insulation layer and outer circumferential insulation layer are formed from a heat-cured prepreg and both of said end insulation layers are formed from a putty-like resin.

7. A resin-molded coil according to claim 3, wherein at least either of said inner circumferential insulation layer and said outer circumferential insulation layer is formed from heat-cured prepreg and said resin layer is formed between said prepreg and said winding.

8. A resin-molded coil according to claim 2, wherein said winding has said obstructing layer disposed on at least one of the surfaces thereof facing to said inner circumferential insulation layer, said outer circumferential insulation layer and said end insulation layer, and said winding has an internal space kept at the atmospheric pressure.

9. A resin-molded coil according to claim 8, wherein at least either of said inner circumferential insulation layer and said outer circumferential insulation layer is formed from heat-cured prepreg and said resin layer formed between said prepreg and said winding.

10. A resin-molded coil according to claim 3, wherein all of said inner circumferential insulation layer, said outer circumferential insulation layer, and said end insulation layers are formed from said resin layer.

11. A resin-molded coil according to claim 8, wherein all of said inner circumferential insulation layer, said outer circumferential insulation layer, and said end insulation layers are formed from said resin layer.

12. A resin-molded coil according to claim 10, wherein one of the end insulation layer in the axial direction of the winding is provided with lead wires and the other end insulation layer is provided with ribs on the surface thereof.

13. A resin-molded coil having a winding, inner and outer circumferential insulation layers formed inside and outside said winding, and end insulation layers formed on the ends in the axial direction of said winding, comprising a resin layer disposed in at least one of said inner circumferential insulation layer, said outer circumferential insulation layer, and said end insulation layers, said resin layer being formed by filling a low-viscosity thermosetting resin composition under atmospheric pressure, followed by heat-curing, terminals connected to said winding and disposed on the surface of said outer circumferential insulation layer, and ribs formed in the vicinity of said terminals.

14. A resin-molded coil having a winding, inner and outer circumferential insulation layers formed inside and outside said winding, and end insulation layers formed on the ends in the axial direction of said winding, comprising a resin layer disposed in at least one of said inner circumferential insulation layer, said outer circumferential insulation layer, and said end insulation layers, said resin layer being formed by filling a low-viscosity thermosetting resin composition under atmospheric pressure, followed by heat-curing, and projecting ribs disposed on the surface of said outer circumferential insulation layer.

15. A method of producing a resin-molded coil comprising the steps of: winding an inner circumferential insulating material on a core, winding a conductor on said inner circumferential insulating material, winding an outer circumferential insulating material on said winding, closing one of the ends in the axial direction of said winding, curing said inner and outer circumferential insulating materials, filling said winding with a low-viscosity thermosetting resin composition, which is composed of a polyfunctional epoxy compound, filler, and a silane coupling agent and titanate coupling agent in a specific ratio for the amount of said filler, under the atmospheric pressure, with said closed end down, heat-curing said resin composition.

16. A method of producing a resin-molded coil comprising the steps of: winding an inner circumferential insulating material on a core, winding a conductor on said inner circumferential insulating material, winding an outer circumferential insulating material on said winding, Q closing one end of the axial direction of said winding with a putty-like resin and forming an obstructing layer on the other end of said winding, curing said inner and outer circumferetial insulating materials, said puttyl-like resin, and said obstructing layer, filling a low-viscosity thermosetting resin composition under the atmospheric pressure, which is composed of a polyfunctional epoxy compound, filler, and a silane coupling agent and titanate coupling agent in a specific ratio for the amount of said filler, into a space formed by said inner and outer circumferential insulating materials, said obstructing layer, and said putty-like resin layer, with said putty-like resin layer down, and heat-curing said resin composition.

17. A method of producing a resin-molded coil comprising the steps of: disposing a winding in a casting mold, with a certain distance apart from said mold inside, casting a low-viscosity thermosetting resin composition, which is composed of a polyfunctional epoxy compound, filler, and a silane coupling agent and titanate coupling agent in a specific ratio for the amount of said filler, into said mold under the atmospheric pressure, heat-curing said resin composition to form resin layers in said winding- and on the inside, outside, and ends of said winding.

18. A method of producing a resin-molded coil comprising the steps of: forming an obstructing layer on the inside and outside surfaces and both ends of a winding so as to prevent the infiltration of liquid resin, disposing said winding in a casting mold, with a certain distance apart from said mold inside, casting a low-viscosity thermosetting resin composition, which is composed of a polyfunctional epoxy compound, filler, and a silane coupling agent and titanate coupling agent in a specific ratio for the amount of said filler, into said mold under the atmospheric pressure, and heat-curing said resin composition, to form resin layers on the inside, outside, and ends of said winding.

19. A method of producing a resin-molded coil comprising the steps of: winding an inner circumferential insulating material on a core, winding a conductor on said inner circumferential insulating material, forming an obstructing layer on at least one of inner circumferential surface, outer circumferntial sursace and end surfaces of said winding winding an outer circumferential insulating material on said winding, closing one end of the axial direction of said inner and outer circumferential insulating materials, curing said inner and outer circumferetial insulating materials and said obstructing layer, filling a low-viscosity thermosetting resin composition under the atmospheric pressure, which is composed of a polyfunctional epoxy compound, filler, and a silane coupling agent and titanate coupling agent in a specific ratio for the amount of said filler, into a space formed by said inner and outer circumferential insulating materials, and heat-curing said resin composition.

20. A method of producing a resin-molded coil comprising the steps of: winding an inner circumferential insulating material on a core, winding a conductor on said inner circumferential insulating material, winding an outer circumferential insulating material on said winding, forming obstructing layers on end surfaces of said winding under the atomospheric pressure, curing said inner and outer circumferential insulating materials and said obstructing layers, filling a low-viscosity thermosetting resin composition under the atmospheric pressure, which is composed of a polyfunctional epoxy compound, filler, and a silane coupling agent and titanate coupling agent in a specific ratio for the amount of said filler,- into a space formed by said inner and outer circumferential insulating materials and - one of said obstructing layers followed by heat curing, and filling said resin composition under the atmospheric pressure, into a space formed by said inner and outer circumferential insulating materials and the other of said obstructing layers followed by heat curing.

21. A resin molded coil substantially as described herein with reference to and as illustrated in the accompanying drawings.

22. A method of producing a resin molded coil substantially as described herein with reference to and as illustrated in the accompanying drawings.

23. A resin composition for use in producing a resin-molded coil comprising a polyfunctional epoxy compound, filler, and a silane coupling agent and titanate coupling agent, the relative proportions of the coupling agents being selected so that the composition has a viscosity at lOO C not substantially greater than 10 poise.

24. A resin composition for use in producing a resin-molded coil comprising a polyfunctional epoxy compound, filler, 0.05-0.3 parts by weight of a titanate coupling agent and 0.3-1.5 parts by weight of a coupling agent.

25. A resin composition according to claim 24 containing not substantially less than 60% filler by weight.

26. A resin composition according to claim 24 or 25 having a viscosity at lOO C not substantially greater than 10 poise.

27. A resin composition substantially as any described and exemplified herein.

28. A resin molded coil according to any of claims 1-14 or 21 wherein said resin layer is produced from a resin composition according to any of claims 23-27.

29. A method accoording to any of claims 15-20 or 22 wherein said resin composition is according to any of claims 23-27.