JP7654412B2 - Electric motor - Google Patents

Description

The present invention relates to an electric motor .

Electrical equipment such as electric motors and transformers used in industry are installed in a wide range of environments, and may be used in environments where water, atmospheric gases, mist, dust, etc. are present. Traditionally, paints for the surface of electrical equipment have mainly been thinner- or polyurethane-based, but these paint films have issues with thickness, strength, and even flexibility. As a result, the paint film is easily damaged by the intrusion of water, atmospheric gases, mist, dust, etc. (hereinafter referred to as flooding, etc.), the impact of dust, etc., and erosion, which may accelerate the progression of corrosion from rust.

Patent Document 1 discloses a method for repairing a liquid tank in which a primer is applied to the painted area and then a sprayable instant-curing resin (such as a polyurea resin) is sprayed onto the painted area.
US Pat. No. 5,399,433 discloses that in an electromagnetic lifter for moving high temperature materials, the coil is insulated from the outside and inside by spray painting with a waterproof product, such as polyurea or other equivalent resin.
Patent Document 3 discloses that a polyurethane-polyurea resin is applied as a protective coating to a CNT-coated flat heater for melting snow and preventing freezing.

JP 2017-101527 A Special Publication No. 2017-519701 JP 2019-125488 A

None of Patent Documents 1 to 3 provides measures to protect electrical equipment such as electric motors or transformers from water intrusion, collisions with dust, corrosion, or rust.

An object of the present invention is to improve the waterproof, dustproof, corrosion-proof and rust-proof effects of an electric motor .

The electric motor of the present invention comprises an electric motor main body having a metal casing, and an output shaft provided on the electric motor main body, the casing comprising an approximately cylindrical housing for accommodating a stator, and a cover provided at an end of the housing for inserting and supporting the output shaft, and is characterized in that a polyurethane layer is provided on the surface of the casing and on the surfaces of fins provided on the casing .

According to the present invention, it is possible to improve the waterproof, dustproof, corrosion-proof and rust-proof effects of the electric motor .

1 is a diagram illustrating an electric motor according to an embodiment; FIG. 1 is a characteristic diagram showing an example of the relationship between elongation and tensile strength of various coatings. FIG. 13 is a diagram for explaining the adhesion of a polyurea layer. FIG. 13 is a diagram showing another type of electric motor according to an embodiment. FIG. 4 is a characteristic diagram showing an example of a temperature change of a coating film during intermittent operation. FIG. 13 is a diagram for explaining an example of applying polyurea to repair a corrosion hole in a coil cover in an electric motor. FIG. 2 is a diagram illustrating a transformer according to an embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[First embodiment]
FIG. 1 shows an electric motor 100, which is an electric device according to an embodiment. In this embodiment, the electric motor 100 is used in a hot rolling line in a steelworks that is constantly exposed to water while operating. As described above, the electric motor 100 used in an environment where water, atmospheric gas, mist, dust, etc. are present has a problem that the coating film is easily damaged by water ingress, collision with dust, etc., and erosion, and corrosion from rust progresses quickly. In addition, if the electric motor 100 has a seam or hole, it is easily susceptible to water ingress, etc.

Therefore, in this embodiment, as described in detail below, a polyurethane layer 106 is provided on the surface of the housing 101a of the motor body 101 of the motor 100.

As shown in FIG. 1, the electric motor 100 comprises an electric motor body 101 having a metal casing 101a made of steel plate or the like, and an output shaft 102 provided on the electric motor body 101. The casing 101a comprises a roughly cylindrical housing 103 that houses a stator, and covers 104 that are detachably provided on both ends of the housing 103 and through which the output shaft 102 is inserted and supported, and has an overall roughly cylindrical shape. In addition, a fixing stand 105 for fixing the electric motor 100 is provided at the bottom of the housing 103.

In such an electric motor 100, a polyurethane layer 106 of a substantially constant thickness is provided on the surface of the housing 101a including the fixed base 105. If the fixed base 105 or the surface of the housing 101a have large irregularities compared to the seams 107 and holes described below, the polyurethane layer 106 of a substantially constant thickness is provided so as to follow the irregularities.
Furthermore, a seam 107 between the housing 103 and the cover 104 is formed on the surface of the casing 101a, and the polyurethane layer 106 is provided so as to cover the seam 107. That is, the polyurethane layer 106 on the housing 103 side and the polyurethane layer 106 on the cover 104 side are continuously connected across the seam 107. Note that, although the seam 107 is used as an example here, if there is a hole in the surface of the casing 101a, the polyurethane layer 106 is provided so as to cover the hole.

On the other hand, no polyurethane layer is provided on the surface of the output shaft 102. The output shaft 102 rotates relative to the motor body 101, and if there was a polyurethane layer that continued continuously from the housing 101a side on the surface of the output shaft 102, the rotation of the output shaft 102 would be hindered. Grease is filled between the bearings in the motor body 101 and the output shaft 102, so water does not seep in between the motor body 101 and the output shaft 102.

Here, polyurea is a resin compound formed by a chemical reaction between isocyanate and polyamine, and has waterproof, dustproof, anticorrosive and rustproof properties.
To form a polyurethane layer 106 on the surface of the housing 101a, polyurethane is applied by brushing, which also serves as painting. At this time, the polyurethane is continuously applied so as to cover the seams 107 on the surface of the housing 101a. When the polyurethane is applied by brushing on the surface of the housing 101a, a measure may be taken such as covering the output shaft 102 with a rag to prevent the polyurethane from getting on it. Although the polyurethane is applied by brushing, it may also be sprayed.

Figure 2 shows examples of the relationship between elongation [%] and tensile strength [MPa] for various coatings. Polyurea is intermediate between the high strength (durability) of epoxy resin and the high elongation (elasticity) of polyurethane, and the polyurea layer can be described as a coating film with highly flexible material properties that include flexibility and stretchability.

In addition, the polyurea layer has a wide heat resistance range of -30°C to 120°C, making it suitable for use in electric motors 100 used in hot rolling lines.

Moreover, the polyurethane layer can maintain high adhesion. The adhesion of the polyurethane layer was examined. As shown in Fig. 3, polyurethane was brushed to a thickness of 1 mm on an iron plate 302 having a hole 301 with a diameter of 30 mm, covering and closing the hole 301, to form a polyurethane layer 303. As shown in Fig. 3(a), hydraulic pressure was applied from the side on which the polyurethane layer 303 was provided (hereinafter referred to as external pressure), and as shown in Fig. 3(b), hydraulic pressure was applied from the side opposite to the side on which the polyurethane layer 303 was provided (hereinafter referred to as internal pressure).
3(b), as the pressure increases, the polyurethane layer 303 gradually expands, and when the pressure reaches 0.24 MPa, peeling begins in the area enclosed by the dotted line in the figure, and the expansion accelerates all at once, resulting in a loss of adhesive strength. Even if the polyurethane layer 303 expands up to about 0.24 MPa, the adhesive strength is covered by the amount of deformation of the polyurethane layer 303, and even if peeling occurs thereafter, the polyurethane layer 303 does not break due to its high flexibility.
On the other hand, in the case of the external pressure shown in Fig. 3(a), the polyurethane layer 303 is pressed against the iron plate 302, and does not expand at all up to 0.70 MPa, resulting in high adhesion. Therefore, when the pressure on one side of the metal surface to which polyurethane is applied is higher than the pressure on the other side, it is preferable to apply polyurethane to the metal surface on the side where the pressure is higher. Considering that only external pressure is applied to the housing 101a of the electric motor 100, it is effective to provide the polyurethane layer 106 for waterproofing, dustproofing, corrosion prevention, and rust prevention on the surface of the housing 101a with seams and holes.

As described above, by providing the polyurea layer 106 on the surface of the housing 101a of the motor body 101 of the motor 100, the effects of waterproofing, dustproofing, corrosion prevention, and rust prevention can be improved. Based on the experience that corrosion and rust can occur not only in water but also in dust, atmospheric gas, mist (including seawater), etc., corrosion and rust prevention experiments were attempted by leaving a steel plate coated with polyurea in various environments. For example, a test steel plate coated with polyurea was placed in an acid mist environment, a scratch was made in the polyurea layer that reached the base metal, and the plate was left for four months. After leaving the plate for four months, the polyurea layer was peeled off and visually inspected, and it was found that rust had spread around the scratch, but that there was no problem with rust prevention under the polyurea layer. In this way, the effectiveness of the polyurea layer in not only waterproofing and dustproofing measures but also corrosion and rust prevention measures was confirmed in the electric motor 100 used in a hot rolling line.

Note that the application of polyurea is not limited to new motors, and it may also be applied to motors in use. Motors are becoming smaller and thinner due to marginal design, and technology to supplement durability through repairs, in other words, maintenance technology for symptoms that do not appear until several years after installation, is expected. For example, if there is a corrosion hole on the surface of the casing of a motor in use, polyurea is applied to repair it. In this way, no tools other than the application of polyurea are required on-site to repair the corrosion hole, and it is possible to cover the corrosion-defected part in a short period of time.

Moreover, the electric motor 100 shown in FIG. 1 is merely one example of an electric motor, and the shape, size, etc. of the electric motor are not limited thereto.
Fig. 4 shows another type of electric motor 400 according to an embodiment. The same components as those of the electric motor 100 shown in Fig. 1 are given the same reference numerals, and their description will be omitted. In the electric motor 400, a housing 101a of the electric motor main body 101 is provided with fins 401 for cooling. In this case, a polyurethane layer 106 of a substantially constant thickness is also provided on the surface of the fin 401. By providing the polyurethane layer 106 on the surface of the fin 401, damage to the fin 401 due to the collision of dust or the like caused by natural cooling air can be prevented.

The difference in thermal conduction was confirmed by repeating intermittent operation of the motor, running for 40 minutes and stopping for 20 minutes, and capturing the ability of the coating to follow temperature changes, between a 1 mm thick polyurea coating and a 0.5 mm thick conventional epoxy anti-corrosion coating. As shown in Figure 5, the polyurea coating and epoxy anti-corrosion coating are synchronized with no temperature difference, responding immediately to the intermittent operation load, and the result was that there was no significant difference in thermal conduction. The temperature transition tendency was the same for fin 401, and findings were obtained that compare favorably not only in thermal conduction but also in heat dissipation.

Second Embodiment
In the first embodiment, a form in which polyurethane is applied to the surface of the housing 101a of the motor body 101 of the motor 100 has been described. However, polyurethane may be applied to other metal surfaces.
An example of applying polyurethane to repair corrosion holes in a coil cover in an electric motor will be described with reference to Fig. 6. A stator 602 supported by a stator frame 601 and a rotor 604 connected to an output shaft 603 are installed in the electric motor. A coil cover 605 is arranged around the stator 602 to protect a coil 602b wound around a stator core 602a.

When a corrosion perforation 606 occurs in the coil cover 605, in order to repair it, polyurea is applied to the area including the corrosion perforation 606 in such a way that it covers and seals the corrosion perforation 606, thereby forming a polyurea layer 607.
If the corrosion perforation 606 is large (e.g., greater than 30 mm in diameter), the corrosion perforation 606 may be blocked with a backing plate 608, and then polyurea may be applied to the area including the backing plate 608 to form a polyurea layer 607.
Although the coil cover 605 is shown as an example, polyurea can also be applied to repair corroded holes in components that do not require vibration resistance, such as partition plates for adjusting the airflow direction and volume inside an electric motor.

When corrosion holes occur in coil covers inside electric motors or partitions for adjusting wind direction and volume, repairing them while they are still installed can have a significant impact on the quality of the insulation, including maintenance powder and welding spatter, and removing and remaking them can affect the process, making it difficult to grasp the damage except during dismantling for repair. For this reason, it is difficult to achieve short repair periods and long repair cycles with conventional repair methods. In contrast, repairs that apply polyurethane as in this embodiment require no tools other than the polyurethane application on site, and it is possible to cover and cover the corroded missing parts in a short period of time.

[Third embodiment]
In the above embodiment, the electric motor is the target, but the electric equipment to which the present invention can be applied is not limited to this, and the present invention may be applied to, for example, a transformer. Fig. 7 shows a transformer 700, which is an example of an electric equipment according to the embodiment. As shown in Fig. 7, the transformer 700 is an oil-filled transformer, and includes a transformer body 701 having a metal housing 701a made of a steel plate or the like, a radiator 702 connected to a side of the transformer body 701, and a conservator 703 connected to an upper part of the transformer body 701.

In such a transformer 700, a polyurethane layer 704 of approximately uniform thickness is provided on the surface of the housing 701a of the transformer body 701, the surface of the radiator 702, and the surface of the conservator 703. In this case, too, if there are large irregularities on the surface of the housing 701a, the surface of the radiator 702, or the surface of the conservator 703, the polyurethane layer 704 of approximately uniform thickness is provided to follow these irregularities. Also, if there are seams or holes on the surface of the housing 701a, the surface of the radiator 702, or the surface of the conservator 703, the polyurethane layer 704 is provided to cover the seams or holes.

The present invention has been described above in conjunction with embodiments, but the above embodiments are merely illustrative examples of how the present invention may be implemented, and the technical scope of the present invention should not be interpreted in a limiting manner based on these embodiments. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features.

100: motor, 101: motor body, 101a: housing, 102: output shaft, 106: polyurea layer, 107: joint, 401: fin, 605: coil cover, 607: polyurea layer

Claims (5)

An electric motor,
The motor includes an electric motor body having a metal housing and an output shaft provided on the electric motor body.
The casing includes a substantially cylindrical housing that houses a stator, and a cover that is provided at an end of the housing and through which the output shaft is inserted and supported,
An electric motor, comprising: a polyurethane layer provided on a surface of the housing and on surfaces of fins provided on the housing . The electric motor according to claim 1, characterized in that the polyurethane layer is provided to cover the joint between the housing and the cover. The electric motor according to claim 1 or 2, characterized in that the surface of the output shaft is not provided with a polyurethane layer. A fixing base is provided on the housing,
4. The electric motor according to claim 1 , wherein the polyurethane layer is provided on a surface of the housing including the fixing base. 5. The electric motor according to claim 1 , which is used in a hot rolling line of a steelworks.

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