JP2011023523A - Electromagnetic steel sheet laminated core which has good thermal conductivity, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve thermal conductivity in the lamination direction of a core (iron core) used for an energy converting electric apparatus such as a motor, generator, and transformer. <P>SOLUTION: Electromagnetic steel sheets used for a core are stacked by bonding across the entire surface through an adhesive layer of ≥0.2 μm and ≤15 μm which is an anaerobic adhesive, with no void generated between the steel sheets. The resulting laminated core has improved thermal conductivity in the lamination direction of the core, with high power. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a core (iron core) used for an energy conversion electrical device such as an electric motor, a generator or a transformer, and more particularly to an electromagnetic steel sheet laminated core and a manufacturing method thereof.

  In electric motors, generators, and transformers, the temperature rises due to iron loss of the core and copper loss of the windings, which is an obstacle to downsizing and high output of iron loss. Therefore, the thermal conductivity of the stator core is important.

The core is formed by laminating electromagnetic steel sheets and is usually fixed by “caulking” or welding. Since electromagnetic steel sheets have a surface roughness on the order of microns, there are micron-order voids between the laminated steel sheets.
Since the thermal conductivity of air filling the air gap is remarkably low (0.03 W / mK), even such a small air gap produces a large thermal resistance.

As a result, a large anisotropy occurs in the thermal conductivity of the core. That is, although the thermal conductivity in the in-plane direction of the steel sheet roughly matches the value expected from the alloy components of the steel sheet (several tens of W / mK), the thermal conductivity in the stacking direction is 1/20 to 1 in the in-plane direction of the steel sheet. It stays around / 7.
Therefore, the heat removal property of the core is significantly inferior to the value expected from the steel alloy component.

  As a measure for improving the thermal conductivity in the core lamination direction, the present inventors have proposed the use of a magnetic steel sheet having a coating (adhesive coating) that exhibits adhesive ability by heating (see Patent Document 1). That is, by laminating magnetic steel sheets with adhesive coating and then heat-bonding, an attempt is made to fill the voids due to the surface roughness of the steel sheets with an adhesive layer as much as possible. The component of the adhesive coat is a resin such as acrylic or epoxy. By this method, the thermal conductivity in the stacking direction can be improved to about 1/5 of the in-plane direction of the steel sheet.

However, there are several difficulties with the adhesive coating method.
One is that in order to secure the strength of the laminate to some extent, it is necessary to secure a thickness of 5 g / m ² or more per side (adhesive layer thickness of 8 μm or more), and the space factor deteriorates. The other is that since the thickness of the adhesive layer cannot be reduced in this way, there is a limit in improving the heat conduction in the stacking direction.
Furthermore, in the case of adhesive coating, the adhesive layer is not completely melted during the heat-bonding process, so that there is a problem that the gap layer is not completely filled.
Therefore, it is difficult to achieve both high thermal conductivity in the stacking direction, space factor, and core stacking strength.

On the other hand, Patent Document 2 proposes a method of filling oil between steel plates.
Specifically, after laminating electrical steel sheets in a container filled with oil, a method of joining the laminate by applying a load in the stacking direction in a state where the steel sheet is taken out of the container or outside the container, or oil is applied In this method, magnetic steel sheets are laminated while a predetermined laminated thickness is reached, and the laminated body is joined by applying a load.
Also in this method, since the gap between the steel plates is filled with oil having a higher thermal conductivity than air, an improvement in the thermal conductivity in the stacking direction can be expected. Moreover, since excess oil can be squeezed out by pressurization, it is possible to suppress deterioration of the space factor due to oil filling and to minimize the influence of thermal resistance.

  However, this method also has drawbacks. Since oil has fluidity, it flows out of the steel sheet, and voids are generated during use, resulting in deterioration of thermal conductivity. Moreover, oil is decomposed and deteriorated due to heat generation of the core, and gas is generated to generate voids, which also causes deterioration of thermal conductivity. Furthermore, since the oil filling the gap does not have the ability to firmly fix the steel plate, another means (such as caulking or welding) for fixing the laminated body is required.

Furthermore, the following publicly known documents exist regarding core lamination using an anaerobic adhesive.
Patent Document 3 discloses a method of laminating a core using an anaerobic adhesive. However, this publication is aimed at reducing the iron loss of the laminated core. Therefore, there is no description in the bonding conditions that can reduce the thermal conductivity in the core lamination direction, in particular, the thickness of the bonding layer.

  Patent Document 4 discloses a method of laminating a core using an anaerobic adhesive. However, this publication aims to reduce the space factor of the laminated core. The core lamination method in this publication is a method in which a recess filled with an adhesive is provided in advance on a part of the steel plate surface, and an anaerobic adhesive is applied only to the recess. Therefore, the entire surface is not bonded, and the effect of improving the thermal conductivity in the stacking direction as in the present invention cannot be exhibited.

  Patent Document 5 describes a core lamination method using an anaerobic adhesive in combination with an effect accelerator. However, since the purpose of adhesion in the publication is simply to fix the laminated steel sheets, the adhesive is applied in a dotted manner only to the teeth portion of the core. Therefore, the entire surface is not bonded, and the effect of improving the thermal conductivity in the stacking direction as in the present invention cannot be exhibited.

JP-A-11-150895 JP 2007-104878 A JP 58-116032 A JP 2006-101629 A JP 2006-334648 A Japanese Patent Publication No.49-6744 Japanese Patent Laid-Open No. 06-33033

  An object of the present invention is to provide a core having a high lamination direction thermal conductivity, a good space factor, and a lamination strength in an electric motor, a generator, and a transformer, and a manufacturing method thereof.

According to the present invention, the anaerobic adhesive is applied to the surface of the magnetic steel sheet in an amount of 0.2 g / m ² or more and 15 g / m ² or less on both sides, and is cured and bonded. By forming the adhesive layer, it is possible to obtain a core having good thermal conductivity in the stacking direction.
If the coating amount of the anaerobic adhesive is less than 0.2 g / m ² per both sides, it becomes impossible to fill the unevenness on the surface of the steel sheet with the adhesive layer, and not only the adhesive strength is lowered but also the thermal conductivity in the laminating direction. to degrade. Moreover, when the application amount of the anaerobic adhesive exceeds 15 g / m ² per both sides, not only the thermal conductivity in the laminating direction is inferior to the weld core, but also the space factor deteriorates and the core loss of the core deteriorates. The characteristics are damaged.

Furthermore, by using a magnetic steel sheet that is not coated with an insulating coating or a magnetic steel sheet that is coated with a phosphate-containing insulating coating, the thermal conductivity in the core stacking direction is improved without sacrificing the stacking strength. Can do.
In the case of an electromagnetic steel sheet provided with another insulating film, the thermal conductivity in the core lamination direction can be improved without sacrificing the lamination strength by using an anaerobic adhesive effect accelerator in combination.

  According to the present invention, the thermal conductivity in the stacking direction of the core is improved, so that the heat removal performance of the core is increased, and it is possible to contribute to high output of a motor or the like.

It is a figure for demonstrating the test piece shape for evaluating the adhesive strength by an anaerobic adhesive agent. It is a figure which shows the lamination | stacking method dependence of the thermal conductivity of the electrical steel sheet laminated core to which the insulating film which mainly has a phosphate was given. It is a figure which shows the lamination | stacking method dependence of the thermal conductivity of the electrical steel sheet laminated core without an insulating film, and the electrical steel sheet laminated core with which the insulating film mainly composed of chromate was given.

Anaerobic adhesive is an adhesive that cures using metal ions such as Fe as a catalyst under oxygen-free conditions. Generally, it does not contain solvents and is used for applications such as screw locking and fitting part adhesion. It is done.
The anaerobic adhesive does not contain a solvent and therefore does not generate gas during curing, and there is no risk of bubbles being generated in the adhesive layer. It is said that the thinner the adhesive layer, the better the adhesive strength. Furthermore, since it hardens | cures under anaerobic conditions, the laminated steel plate inside can also be adhere | attached properly.
From the above, the inventors can (a) sufficiently bond the steel plate with an adhesive layer thickness of micron order without causing a gap between the laminated steel plates, and (c) in the stacking direction of the laminated core. We thought that thermal conductivity could be improved. These predictions were confirmed by the following procedure.

First, laminated electromagnetic steel plates of the two 10 cm × 10 cm in anaerobic adhesive double-sided per 2 g / m ^2, after curing, observation of the bonding conditions of the cross-section, become entirely bonded state without expected bubbles Turned out to be.

  Anaerobic adhesives are said to require the presence of metal ions upon curing. On the other hand, the electrical steel sheet is usually provided with an insulating film on the surface. Therefore, when an electrical steel sheet with an insulating film is bonded with an anaerobic adhesive, it may not be bonded.

  Therefore, the dependence of the adhesive strength on the insulating film was investigated. Electrical steel sheet A not provided with an insulating film, Electrical steel sheet B provided with an insulating film mainly composed of chromate described in Patent Document 6 and the like, Insulating film mainly composed of phosphate described in Patent Document 7 and the like Prepare three types of electrical steel sheet with magnetic steel sheet C, and make an adhesion test piece (adhesion layer thickness 2 μm) as shown in Fig. 1 with anaerobic adhesive, and increase the adhesive strength by tensile test. It was measured.

  In the case of adhesion, anaerobic adhesive is applied after using anaerobic adhesive alone, and after applying and drying a curing accelerator for anaerobic adhesive mainly composed of copper salt and aliphatic amine before applying the adhesive. Two cases were evaluated when they were bonded together.

  As shown in Table 1, the electrical steel sheet to which the insulating film mainly composed of phosphate was applied exhibited substantially the same adhesive strength as the electrical steel sheet without the insulating film. That is, it can be said that the electrical steel sheet provided with an insulating film mainly composed of phosphate has an advantage that it can be bonded with an anaerobic adhesive without using a curing accelerator. Even in the case of an insulating film mainly composed of chromate, sufficient adhesion strength can be obtained by using a curing accelerator in combination.

  The reason why the effect promoter is not necessary in the case of an insulating film mainly composed of phosphate is not clear. Perhaps it is imagined that the phosphate and steel plate react during film formation, and that the film contains something like an iron phosphate compound, and the iron phosphate compound has the effect of promoting the effect. I think that.

  Next, although it is confirmation of the heat conductivity improvement effect of the lamination direction by an anaerobic adhesive, this is demonstrated in an Example.

Example 1
A JIS standard 35A300 electrical steel sheet having an insulating film mainly composed of phosphate was prepared. From the former electromagnetic steel sheet, a caulked and laminated core, a welded and laminated core, a core that was laminated and bonded with an anaerobic adhesive, and a core that was applied with an adhesive coat and was pressure-bonded and bonded were prepared.
In the case of an adhesive core made of an anaerobic adhesive, an anaerobic adhesive applied amount was changed in a range of 0.15 to 25 g / m ² per both sides. In the case of an adhesive core with an adhesive coat, a coating with the adhesive coat applied amount changed in the range of ² to 20 g / m ² was prepared. For measuring the thermal conductivity of the core, a hot disk method that can evaluate both the steel sheet lamination direction and the in-plane direction of the laminated core was used.

FIG. 2 shows the results obtained by the above experiment. From the figure, the following can be read first.
In the laminated core, the thermal conductivity in the laminating direction is inferior to the thermal conductivity in the in-plane direction. The in-plane thermal conductivity is less dependent on the laminating method or decreases slightly with increasing adhesion layer due to anaerobic adhesives and adhesive coats.
The thermal conductivity in the stacking direction increases with a decrease in the adhesive layer, but deteriorates again when the adhesive layer is extremely small (less than 0.2 g / m ^{2 on} both sides). If the amount of the adhesive is extremely small, it is considered that it becomes difficult to fill the unevenness of the steel plate with the adhesive to form an adhesive layer without a void. When compared with the same amount of adhesive used, the anaerobic adhesive has a greater thermal conductivity in the stacking direction than the adhesive coat.

The following can be read by comparing with the welding core.
In the core by the adhesive coat, in order to obtain better thermal conductivity in the stacking direction than the weld core, the coating amount of the adhesive coat needs to be 8 g / m ² or less per both sides. However, in this region, the adhesive strength generally decreases. It is difficult to achieve both improved thermal conductivity and core strength.
On the other hand, in the case of bonding with an anaerobic adhesive, improvement is recognized from the weld core at an application amount of 15 g / m ² or less per both sides of the adhesive, and as mentioned above, at least an adhesive application amount of 2 g / m. Even ^{2 has} sufficient adhesive strength.

Therefore, the adhesive core made of the anaerobic adhesive can satisfy the adhesive strength and the high lamination direction thermal conductivity. The reason why the adhesive lamination by the adhesive coat has a lower thermal conductivity in the laminating direction than the adhesive lamination by the anaerobic adhesive is presumed to be due to the presence of voids in the adhesive layer of the adhesive coat. The
FIG. 2 also shows that the thermal conductivity in the laminating direction deteriorates more than the weld core when the application amount of the anaerobic adhesive is less than 0.2 g / m ^{2 on} both sides. Note that the density of the anaerobic adhesive after curing is about 1.1, and the coating amount of 15 g / m ² per both sides corresponds to the adhesive layer thickness of 15 μm.

(Example 2)
Prepare a JIS standard 35A300 electrical steel sheet without an insulating film and a JIS standard 35A300 electrical steel sheet with an insulating film mainly composed of chromate. From the latter steel plate, a curing accelerator for anaerobic adhesive composed mainly of a copper salt and an aliphatic amine was applied and dried in advance, and then a core laminated and adhered with an anaerobic adhesive was prepared. In any case, the application amount of the anaerobic adhesive was changed in the range of ^{2 to} 25 g / m ² per both sides.
As a core for comparison, a weld core made from a magnetic steel sheet of JIS standard 35A300 provided with an insulating film mainly composed of chromate was used.
For measuring the thermal conductivity of the core, a hot disk method that can evaluate both the steel sheet lamination direction and the steel sheet in-plane direction in the laminated core was used.

FIG. 3 shows the results obtained by the above experiment. From the figure, even in the case of an electromagnetic steel sheet without an insulating film and an electromagnetic steel sheet with an insulating film mainly composed of chromate, adhesive lamination using an anaerobic adhesive with an adhesive application amount of 15 g / m ² or less. Thus, it can be seen that a core having excellent thermal conductivity in the stacking direction can be obtained. In addition, in the case of electrical steel sheets coated with an insulating film mainly composed of chromate, it was mentioned before that sufficient adhesive strength can be obtained by applying and drying the curing accelerator for anaerobic adhesive before bonding. It is as follows.

Claims (6)

  A laminated core having good thermal conductivity, characterized in that electromagnetic steel sheets are laminated and fixed without forming a void through an adhesive layer of 0.2 μm or more and 15 μm or less.   The laminated core having good thermal conductivity according to claim 1, wherein an adhesive layer without an air gap is formed using an anaerobic adhesive. The anaerobic adhesives, double-sided coated at 0.1 g / m ² or more per side 7.5 g / m ² or less in the electromagnetic steel sheets, or one surface coated at 0.2 g / m ² or more per side 15 g / m ² or less in the electromagnetic steel sheets A method for producing a laminated core having good thermal conductivity, characterized in that electromagnetic steel sheets are bonded and laminated.   The method for producing a laminated core having good thermal conductivity according to claim 3, wherein an electromagnetic steel sheet not provided with an insulating coating is used.   The method for producing a laminated core having good thermal conductivity according to claim 3, wherein an electromagnetic steel sheet coated with an insulating coating containing a phosphate is used.   The laminated core having good thermal conductivity according to claim 3, wherein after applying and drying the effect promoter for anaerobic adhesive in advance, the magnetic steel sheet is bonded and laminated using the anaerobic adhesive. Production method.

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