JP2991550B2 - Insulation method for rotating electric machine winding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for insulating windings of a rotating electric machine such as a cage-type polyphase induction motor used for an automobile.

[0002]

2. Description of the Related Art Electric rotating machines for electric braking are widely known as rotating electric machines for automobiles. In this device, electric energy generated from a rotating electric machine during braking is consumed by a resistor to maintain a high braking force.

In order to obtain the highest possible magnetic flux in a given narrow space, a so-called turbulent winding method in which an enamel wire is wound many times is most suitable for the winding of a rotating electric machine used in this device. is there.

The windings of the rotating electric machine are not deformed by running vibrations or electromagnetic vibrations during rotation, the insulation is destroyed, and the wires are not broken by fatigue. In order to protect the enamel wire from moisture and rainwater contained in the resin, the resin may be impregnated with a resin such as epoxy, cured and fixed.

[0005]

However, the windings used in the rotating electrical machine for automobiles are repeatedly subjected to braking, so that the temperature is rapidly increased and decreased, so that a so-called heat cycle is applied. For this reason, cracks occur in the resin and enamel coating due to fatigue caused by the thermal stress caused by the difference in the thermal expansion coefficient between the conductor, enamel coating, impregnated resin and iron core, deteriorating insulation, and in some cases, the windings are burnt out due to short-circuiting There was something to do.

On the other hand, since there is a large demand for rotating electrical machines for automobiles, windings used for this purpose are manufactured in large quantities. Therefore, windings are wound by a machine and inserted into a slot of an iron core.
At that time, there has been a problem that insulation is damaged by rubbing by a machine and insulation properties are deteriorated.

[0007] For this reason, in the winding of the rotating electric machine for an automobile, insulation that is not easily deteriorated due to fatigue caused by thermal stress caused by a difference in the coefficient of thermal expansion between the conductor and the enamel coating due to repetition of rising and falling temperatures. Is required, and the required functions can be exerted even when moisture or rainwater enters the rotating electric machine, and can withstand vibration during traveling.
Further, the development of a winding capable of mechanical winding is desired.

The present invention is excellent in heat cycle resistance capable of withstanding a sudden rise and fall temperature, and can exhibit required functions even when moisture or rainwater enters, and can withstand vibration. An object of the present invention is to provide a method of insulating a winding of a rotating electric machine that can be manufactured.

[0009]

The present invention has the following features to attain the above object. The invention corresponding to claim 1 is to apply a polyimide varnish of pyromellitic dianhydride type multiple times to the outer peripheral surface of the copper wire and bake it, and then apply and bake a polyamide imide varnish at least once on the enamel. A method for insulating windings of a rotating electric machine, wherein a polyamide-imide overcoated polyimide insulated wire having a film formed thereon is wound around a rotating electric machine core.

According to a second aspect of the present invention, a polyimide varnish of pyromellitic dianhydride type is applied and baked multiple times on the outer peripheral surface of a copper wire, and then a polyamide imide varnish is applied and baked at least once thereon. A polyamide-imide overcoated polyimide insulated wire having an enamel film formed thereon is wound around a rotating electric machine core, and then further impregnated with a thermosetting resin, and then cured. . The invention corresponding to claim 3 is a method of insulating a rotating electrical machine winding using an epoxy resin containing an acid anhydride as the thermosetting resin according to claim 2.

[0011]

According to the present invention, an enamel film obtained by applying and baking a polyimide varnish of pyromellitic dianhydride type multiple times has excellent adhesion to a copper wire,
Since the change of the coefficient of linear expansion with temperature is small up to ° C., it follows the rapid rise and fall of the temperature of the conductor, and the enamel film hardly peels off from the conductor. In addition, even if cracks occur in the impregnated resin in contact with the enamel film due to the toughness of the film, the enamel film made of this pyromellitic dianhydride type polyimide has a feature that cracks hardly penetrate.

Since the polyamideimide varnish has excellent friction resistance, it protects the polyimide film, and when the winding is machine-wound, there is little occurrence of insulation damage due to friction with the machine. Excellent insulation properties.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the drawings. Here, windings used in a rotating electric machine for an automobile will be described by way of an example. FIG. 1 is a cross-sectional view of a polyamide-imide overcoated polyimide insulated wire 4 obtained by the insulation method according to the embodiment of the present invention. The following formula is applied to the outer peripheral surface of the soft copper wire 1 for electricity.

[0014]

Embedded image

A polyimide varnish of the pyromellitic dianhydride type (polypyromellitic dianhydride type) shown in the above is applied and baked multiple times to obtain a pyromellitic dianhydride type polyimide film 2 and then from above. A polyamide-imide overcoated polyimide insulated wire 4 in which a polyamide-imide film 3 is formed by applying and baking a polyamide-imide varnish at least once.

The insulated wire 4 is wound around an iron core formed by laminating a magnetic steel plate (not shown) via a predetermined slot insulation and an interphase insulation, and a yarn binding for preventing vibration is applied to an end portion of the winding. Thereafter, the winding is impregnated with an epoxy resin composition containing an acid anhydride curing agent containing no solvent and cured by heating.

The following effects are obtained by using such an insulating method. In other words, the enamel coating obtained by applying and baking a pyromellitic dianhydride type polyimide varnish multiple times has excellent adhesion to copper,
Since the change in the coefficient of linear expansion due to temperature is small up to 0 ° C., it can well follow the rapid rise and fall of the temperature of the conductor due to the braking of the automobile, and the enamel film does not easily peel off from the conductor. In addition, since the film is tough, even if cracks occur in the impregnated resin in contact with the enamel film, the enamel film made of the pyromellitic dianhydride type polyimide has a feature that cracks hardly penetrate.

FIG. 2 shows a reciprocating wear test of the enameled wire of the polyimide film A (pyromellitic dianhydride type) and the enameled wire of the polyamide film B (pyromellitic dianhydride type) obtained by the above-mentioned insulation method. FIG. The enameled wire used here was a copper wire having a diameter of 1 mm and an enamel coating having a thickness of 38 μm, according to JIS C 3003.
A reciprocating abrasion test was performed according to
It is the result of having changed up to. As is clear from this figure, the polyamide film B is much more excellent in abrasion resistance than the polyimide film A. Therefore, the polyamide-imide film of the above-described embodiment protects the pyromellitic dianhydride type polyimide film, and when the winding is machine-wound, the occurrence of insulation damage due to friction with the machine is small, and the completed rotating electric machine It can be seen that the insulation properties as the winding are excellent.

Next, a specific example of this embodiment will be described. A 1 mm-diameter soft copper wire for electricity is coated with a pyromellitic dianhydride type polyimide varnish having the above-mentioned chemical structure so as to have a thickness of about 5 μm at a time, and heated at 400 to 450 ° C. (hereinafter referred to as a furnace). Is called)
The process of heating and curing by passing through is repeated six times to form a polyimide film having a thickness of 30 μm, and then a polyamideimide varnish is further applied once from above, and then passed through a furnace at 400 to 450 ° C. In this way, by heating and curing, a polyamide overcoat polyimide insulated wire having a thickness of about 35 μm as a whole is obtained. In order to examine the effect of the enameled wire thus obtained, heat-resistant insulated wires of Comparative Examples 1, 2, 3, and 4 as shown in Table 1 were prepared.

[0020]

[Table 1] That is, Comparative Example 1 is a benzophenone tetracarboxylamide hydride type polyimide insulated wire having a chemical structure represented by the following formula.

[0021]

Embedded image Comparative Example 2 is a polyesterimide insulated wire having a three-dimensional network structure constituted by imide bonds and ester bonds. Comparative Example 3 is an insulated wire in which polyamideimide was applied on an unfired ceramic layer, and further, poreimide was applied and baked thereon. Comparative Example 4 is an insulated wire in which a polyborosiloxane-based polymer was further coated and baked with polyester.

Next, this polyamide overcoated polyimide insulated wire and the insulated wire of the comparative example were separately applied to a core formed by laminating magnetic steel sheets, and aramid paper having a predetermined thickness of 125 μm and a polyimide film having a thickness of 125 μm were applied. Winding is performed through slot insulation and interphase insulation made of a combined insulating sheet, and the ends of the windings are bound with epoxy prepreg glass thread to prevent vibration.

Next, the winding was impregnated with a solvent-free epoxy resin composition containing an acid anhydride curing agent and a solvent-type phenol-modified alkyd varnish in combination with the insulated wire shown in Table 1. Heating was performed at 130 ° C. for 5 hours (5 hours), and then at 155 ° C. for 15 hours (1 hour).
5h) Heat and thereby cure.

The acid anhydride curing agent-containing epoxy resin composition not containing a solvent used here was Epicoat 828.
It comprises 80 parts by weight (trade name of Shell), 20 parts by weight of DEN431 (trade name of Dow Chemical Company), 75 parts by weight of Epicron B570 (trade name of Dainippon Ink Co., Ltd.), and 1 part by weight of benzyldimethylamine. Solvent-type phenol-modified alkyd varnish is manufactured by Toshiba Chemical Corporation.
VB-2319 was used.

The rotating electric machine in which the windings are insulated is configured for electric control of an automobile, and a running test is repeated. As a result, the rotating electric machines in which the insulation is provided in the comparative examples are relatively short. Although the windings were burned at the running distance, no abnormality occurred in the product of the present invention even after long distance running.

Therefore, in order to confirm these results,
Twisted pair of enameled wires (twisted pair) according to JISC 3003 in the combinations shown in Table 1 are impregnated with resin or varnish and cured to prepare a sample, and this sample is placed in an oven at 240 ° C and 40 ° C. The heat cycle shown in FIG. 3 was given by reciprocating between the enamel wires, and the change in the dielectric breakdown voltage (BDV) between the enamel wires after absorbing the moisture for 48 hours at 100% relative humidity after completion of a certain cycle was examined. The results are shown in FIG. 4. As shown in FIG. 4, the insulation of the present invention showed the least decrease in the dielectric breakdown voltage due to the heat cycle, and corresponded well to the result of the running test using the test vehicle.

When the cross section of the sample after the heat cycle test using the above-mentioned twisted pair was photographed by a scanning electron microscope, cracks generated in the resin in any of the comparative examples penetrated the enamel film as they were and corroded the conductor. On the other hand, in the configuration of this example, it was found that cracks generated in the resin proceeded along the interface between the resin and the enamel film, did not easily penetrate the enamel film, and therefore did not cause corrosion of the conductor. .

Then, the dimensional changes of the above-mentioned copper wire, the above-mentioned comparative examples 1, 2, 3, and 4 and the insulating film and the impregnated resin of the insulated wire of this example were measured, and the glass transition temperature was measured. The linear expansion coefficient α was determined from a region where the temperature change in dimensions was linear around Tg. Table 2 shows the measurement results of the linear expansion coefficient α and the glass transition temperature Tg.

[0029]

[Table 2]

As is apparent from Table 2, the polyimide insulated wire of the pyromellitic dianhydride type used in the present embodiment has a smaller dimensional change in the glass transition temperature Tg region than the other insulated wires. And as can be seen from Table 2, the coefficient of linear expansion α around the glass transition temperature Tg
It can be seen that there is a small change of 1 and that the dimensional change is relatively close to copper over a wide temperature range from room temperature to 400 ° C., and can follow the dimensional change of copper. In Table 2, α1 is the coefficient of linear expansion below the glass transition temperature Tg, and α2 is the coefficient of linear expansion above the glass transition temperature Tg.

Similarly, the epoxy resin composition R ₁ containing an acid anhydride curing agent containing no solvent has a smaller dimensional change in the glass transition temperature Tg region than the solvent-type phenol-modified alkyd varnish R ₂ and has a wider range. It was found that there was no significant dimensional change over the temperature range. It is considered that these are the reasons why the insulation method of this example exhibited excellent heat cycle resistance.

As described above, the insulating method according to the embodiment of the present invention has excellent heat cycle resistance.
Therefore, the temperature rise of the rotating electric machine can be increased,
High reliability can be obtained because the operation can be performed without burning by repeated rapid temperature changes. In the embodiment described above, the rotating electric machine winding used for the electric braking of the automobile is taken as an example. However, the present invention is not limited to this, and the rotating electric machine winding for other uses may be used.

[0033]

According to the method for insulating windings of a rotating electric machine of the present invention, even if the windings are automatically wound by a machine, there is little insulation damage due to rubbing with the machine, and the heat resistance of the completed winding insulation. Because of its excellent heat resistance and heat cycle resistance, a strong braking force can be obtained without burnout of the insulation by repeated rapid temperature changes, and energy can be used effectively.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an insulated wire used in the present invention.

FIG. 2 is a diagram showing the results of a wear test of an enameled wire.

FIG. 3 is a view showing conditions of a temperature change in a heat cycle test performed to evaluate the heat cycle property of insulation of the insulated wire of FIG. 1;

FIG. 4 is a view showing a result of a heat cycle resistance evaluation test of the insulated wire of FIG. 1;

[Explanation of symbols]

1 ... Soft conductive wire for electric power, 2 ... Polypyromellitic dianhydride type polyimide coating, 3 ... Polyamideimide coating, 4 ... Polyamideimide overcoated polyimide insulated wire.

Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI H01F 5/06 H01F 5/06 Q H02K 3/30 H02K 3/30 15/12 15/12 C (58) Field surveyed (Int.Cl. ⁶ , DB name) H01B 13/00 517 H01B 3/30 H01B 7/02 H01B 13/16 H02K 15/00-15/16

Claims (3)

(57) [Claims] 1. An outer enamel coating is formed by applying and baking a polyimide varnish of pyromellitic dianhydride type multiple times on the outer peripheral surface of a copper wire, and then applying and baking a polyamide imide varnish at least once thereon. A method for insulating windings of a rotating electric machine, wherein a polyamide-imide overcoated polyimide insulated wire is wound around an iron core of the rotating electric machine. 2. An enamel film is formed by coating and baking a polyimide varnish of pyromellitic dianhydride type multiple times on the outer peripheral surface of a copper wire, and then coating and baking polyamide varnish at least once thereon. What is claimed is: 1. A method for insulating a winding of a rotating electrical machine, comprising: winding a polyamide-imide overcoated polyimide insulated wire around a rotating electrical machine core, and further impregnating and curing the thermosetting resin. 3. The method according to claim 2, wherein an epoxy resin containing an acid anhydride is used as the thermosetting resin.