JP2010029035A - Electrodeposition coating component for motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrodeposition coating component for a motor capable of suppressing the formation of a projection where a film is locally largely projected around a negative electrode member and capable of satisfactorily solving a problem caused by the existence of the projection, when components for a motor are subjected to cation electrodeposition coating. <P>SOLUTION: The surface is subjected to cation electrodeposition coating. The film of coating has a volume resistivity of ≥5×10<SP>15</SP>Ω cm at the temperature of 23°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrodeposition-coated component for a motor in which cationic electrodeposition coating is applied to the surface of a ring magnet, a stator core or the like used as a rotor magnet of a spindle motor.

Conventionally, a ring magnet has been widely used as a rotor magnet of a spindle motor that constitutes a rotational drive unit of a personal computer (PC), a mobile phone, a digital video camera, or the like.
For example, Patent Document 1 below discloses an example of a spindle motor using this type of ring magnet.

FIG. 2 shows a spindle motor disclosed in Patent Document 1. In FIG. 2, reference numeral 200 denotes a spindle motor, 202 and 204 denote a fixed-side motor base and stator, and 203 denotes a cylindrical shape on the motor base 202 side. A rising portion 205 is a stator core. The stator core 205 is fitted and assembled to the rising portion 203 in an external fitting state.
Reference numeral 206 denotes a hub that rotates with a disk mounted thereon. A ring magnet 208 made of a permanent magnet is held in the hub 206 in an integrally rotated state.
Here, the ring magnet 208 is fitted into the back yoke ring 210 in an internally fitted state, and is bonded and fixed with an adhesive, and is assembled to the hub 206 via the back yoke ring 210.

  Conventionally, rare earth magnets such as Nd-Fe bond magnets and sintered magnets have been used as rotor magnets for spindle motors such as HDD (Hard Disk Drive) devices. However, these magnets have a problem that they tend to generate rust. Therefore, it is used after electrodeposition coating, usually cationic electrodeposition coating, for rust prevention.

  Cationic electrodeposition coating involves immersing an object (ring magnet, stator core, etc.) in an electrodeposition coating liquid (usually an epoxy resin coating liquid), applying a voltage between the anode and the anode, and applying a direct current. By flowing, the positively charged paint particles in the paint liquid migrate to the cathode side, and the paint particles are deposited on the surface of the object to be coated to form a coating. As shown in FIG. 3, the cathode member 212 having the claw 211 having a sharp tip is usually a ring magnet (in this stage, since the ring magnet is not yet magnetized, it is strictly a magnet molded body. ) Is gripped on the outer peripheral surface side and is subjected to cationic electrodeposition coating.

  However, when cationic electrodeposition coating is applied to the ring magnet 208 in this way, as shown in the partial enlarged view of FIG. As a result, the protrusion 214 was formed on the ring magnet 208, and this phenomenon was a big problem in the cationic electrodeposition coating of the ring magnet 208.

During the cationic electrodeposition coating, the coating formed by the deposition of paint particles on the surface of the ring magnet 208 subsequently grows and gradually increases the film thickness. As a result, the electrical resistance of the coating itself increases. go.
As a result, new deposition of paint particles on the thickened film is suppressed, and instead, paint particles are preferentially deposited on thin or thin film. Then, the entire film is formed.

  This is the basic behavior of the paint particles during the cationic electrodeposition coating, and the process of forming the coating. However, the potential is locally high in the vicinity of the contact portion of the cathode member 212 to the ring magnet 208, and this is the reason. In the past, it was inevitable that the protrusions 214 were formed around the cathode member 212.

  The electrodeposited ring magnet 208 is then fitted into the back yoke ring 210 and assembled to the back yoke ring 210 after the coating is cured (baked). If the projection 214 remains on the magnet 208, the projection 214 becomes an obstacle when the ring magnet 208 is fitted to the back yoke ring 210, causing various problems as follows.

  That is, when there is no such protrusion 214, the ring magnet 208 is brought into close contact with the back yoke ring 210 without any gap as shown in FIG. 208 can be fitted to the back yoke ring 210, and the gap S as set between the ring magnet 208 and the stator 204, specifically the stator core 205, can be well formed. If 214 remains, the projection 214 inhibits the close contact between the ring magnet 208 and the back yoke ring 210 as shown in (b), and the ring magnet 208 is formed on the projection 214. This will cause partial distortion and deformation at the location.

  Thus, when such distortion and deformation occur, when the ring magnet 208 magnetized during the operation of the spindle motor rotates at a high speed, the distance (gap S) between the ring magnet 208 and the stator 204 becomes the ring magnet 208. , The balance between the repulsion and attraction force between the magnetic field induced by the stator 204 and the ring magnet 208 is lost.

  In recent years, devices such as HDD devices have been increasingly reduced in size and increased in capacity, and the rotational speed of the spindle motor has also been increased. In this case, the above-mentioned protrusion 214 is subject to vibrations and abnormalities during motor rotation. This may cause sound generation and malfunction in data processing.

  Further, the gap S between the ring magnet 208 and the stator 204 is very small. If the ring magnet 208 is deformed so as to partially protrude inward by the projection 214, the ring magnet 208 and the stator 204 are deformed. There is also a possibility that 204 may come into contact with the rotation.

  In addition, if the projection 214 as described above is generated, the ring magnet 208 is assembled with the back yoke ring 210 in an off-center state when the ring magnet 208 is fitted to the back yoke ring 210. This also causes vibration of the motor, abnormal noise, or malfunction in data processing.

The point that the protrusion 214 is formed when electrodepositing the ring magnet 208 is specifically pointed out in the above-mentioned Patent Document 1 and the following Patent Document 2, and the means for solving them is described in Patent Document 1. , Patent Document 2.
However, these Patent Documents 1 and 2 do not specifically point out or solve the problem that the ring magnet 208 may be distorted or deformed by the protrusions 214, thereby adversely affecting the operation of the motor. Also in terms of means, those disclosed in Patent Document 1 and Patent Document 2 are different from the present invention.

  On the other hand, the stator core 205 as a motor component is formed by stacking soft magnetic steel plates excellent in magnetic permeability, punched into a shape having a plurality of comb teeth as shown in FIG. This stator core 205 is also used after being subjected to cationic electrodeposition coating in order to prevent rusting on the steel sheet.

In the case of the cationic electrodeposition coating of the stator core 205, the inner peripheral surface of the stator core 205 is held by the sharply pointed claws 211 of the cathode member 212, and the cationic electrodeposition coating is performed.
In this case as well, as shown in FIG. 6B, the coating particles are excessively deposited around the claw 211 of the cathode member 212 and the projection 214 is formed on the coating.

  The electrodeposited stator core 205 is externally fitted to the rising portion 203 of the motor base 202 after being cured, and is assembled to the motor base 202. At this time, the above-described protrusion 214 remains on the stator core 205. If this is the case, when the stator core 205 is fitted to the rising portion 203 and assembled, the projection 214 impedes the assemblability and causes misalignment as in the case of the ring magnet 208. This may cause deterioration in the positional accuracy of the assembly.

  Further, depending on the case, the protrusion 214 may break due to the force at the time of assembly, and the broken minute piece 220 may fall off during high-speed rotation of the spindle motor, causing problems such as abnormal noise or vibration of the motor. .

  Although the ring magnet and the stator core have been described above, in other electrodeposition coated parts for motors, the formation of the protrusions 214 deteriorates the assembling property and the positional accuracy of the assembling, thereby adversely affecting the operation of the motor. The same problem as the above ring magnet and stator core occurs.

In addition, the following problems have conventionally occurred in the electrodeposition coating parts for motors.
For example, in the cationic electrodeposition coating of the ring magnet 208, the surface opposite to the surface gripped by the cathode member 212, for example, the outer peripheral surface side and the inner periphery of the ring magnet 208 as shown in FIG. There arises a problem that the film thickness difference occurs between the surface and the film, that is, the film thickness is thick on the outer peripheral surface side and the film thickness is thin on the inner peripheral surface side. When it is going to secure thickness, the film thickness of the coating film becomes excessively thick on the outer peripheral surface side, which deteriorates productivity and consumes paint more than necessary.
This also applies to other electrodeposition coated parts other than the ring magnet.

JP-A-8-170192 Japanese Patent Application Laid-Open No. 10-285881

  In the background of the above circumstances, the present invention can suppress the formation of protrusions in which the coating locally protrudes largely around the cathode member when cationically electrodepositing a motor component such as a ring magnet, The object of the present invention is to provide an electrodeposition coated part for a motor that can satisfactorily solve the problems caused by the presence of the protrusions and can equalize the film thickness of the coating.

Thus, the first aspect is characterized in that the surface is subjected to cationic electrodeposition coating and the volume resistivity of the coating film is 5 × 10 ¹⁵ Ω · cm or more at a temperature of 23 ° C.

Effects and effects of the invention

As described above, the electrodeposition coating part for motors of the present invention has a surface subjected to cationic electrodeposition coating, and the volume resistivity of the electrodeposition coating film is 5 × 10 ¹⁵ Ω · cm at a temperature of 23 ° C. The one having the above resistance, that is, one having a remarkably higher electric resistance than the conventional one.
According to the present invention, it is possible to effectively suppress the protruding height of the protruding portion around the cathode member that occurs during the cationic electrodeposition coating, thereby favorably solving the various problems described above due to the presence of the protruding portion. Can be solved.

In the present invention, as described above, the volume resistivity of the electrodeposition coating film is set to a high resistance, thereby suppressing the formation of protrusions locally generated around the cathode member. The reason is as follows.
As described above, a coating grows during cationic electrodeposition coating, and when the thickness increases, the electrical resistance of the coating itself increases, and when a certain film thickness is reached, an equilibrium state is reached. The new deposition is suppressed, and the film growth is substantially stopped.
Correspondingly, the deposition of coating particles at other locations and the formation and growth of coatings proceed accordingly.

However, the conventional cationic electrodeposition coating has a small volume resistivity of about 10 ¹³ to 10 ¹⁴ Ω · cm, and therefore the thickness of the coating is thick when the film formation is in an equilibrium state and the film growth stops. It will be a thing. That is, when the film grows greatly and becomes thicker, it is in an equilibrium state for the first time.
Therefore, if the electrodeposition coating is completed in the meantime, a portion where the coating particles are naturally deposited and a portion where the deposition is little occur.
It is thought that the formation of the protrusions is caused by that.

However, in the present invention, the volume resistivity of the film is as high as 5 × 10 ¹⁵ Ω · cm or more, and therefore, in the cationic electrodeposition coating, the above equilibrium state is reached at an early stage of the film growth of the film. Film growth stops when the film thickness is thinner than before, and instead, film generation and growth at other locations is promoted.

In other words, the growth of the projection stops at the stage where the projection height of the projection is low, and the generation and growth of the film at another location is promoted instead of the growth of the projection. It is.
As a result, according to the present invention, the protrusion height of the protrusion around the cathode member can be effectively reduced, and a motor component such as a ring magnet is gripped by the cathode member on the outer peripheral side and the electric power is supplied. When the coating is applied, the difference in film thickness between the outer peripheral surface side and the inner peripheral surface side can be reduced.

In the present invention, if the volume resistivity is less than 5 × 10 ¹⁵ Ω · cm, the effect of the present invention cannot be exhibited sufficiently.
On the other hand, if the volume resistivity is larger than 5 × 10 ¹⁷ Ω · cm, it is difficult to form a film of electrodeposition coating, it takes a long time for electrodeposition coating, productivity is lowered, and cost is increased. Therefore, it is desirable to set the upper limit to 5 × 10 ¹⁷ Ω · cm.

The present invention can be applied to various ring magnets when applied to a ring magnet as a motor component.
For example, a rare earth-iron ring magnet, specifically, Nd—Fe—B or Sm—Fe—N magnetic powder is pulverized and adjusted to a predetermined particle size, mixed with a thermosetting resin or a thermoplastic resin binder, and compressed. Rare earth-iron-based bonded magnet obtained by molding or injection molding, or rare earth-Fe-based obtained by orienting crystal grains while pressing Nd-Fe-B or Sm-Fe-N magnetic powder at high temperature Hot-worked magnets or Nd-Fe-B or Sm-Fe-N-based alloy ingots are finely pulverized, crystallographically oriented in a magnetic field, and then sintered to obtain rare earth-iron-based sintered magnets. Can be applied.

In the case of these rare earth magnets, there is a problem that rust is particularly likely to occur. Therefore, the effect of the present invention is high when applied to these magnets, but the present invention can be applied to various other ring magnets. It is.
In addition, the stator core as a motor part can be suitably applied to a laminated steel sheet made of silicon steel, low carbon steel, or pure iron, punched into a shape having a plurality of comb teeth corresponding to the number of poles. .

Next, embodiments of the present invention will be described in detail below.
"Manufacture of bonded magnet A"
Nd-Fe-B ultra-quenched magnetic powder MQP-B manufactured by Magnequench International Co., Ltd. is pulverized with a vibrating ball mill to an average particle size of 110 μm, and this is surfaced with a silane coupling agent manufactured by Toray Dow Corning Co. Processed.
This was mixed with a cresol novolac type epoxy resin (number average molecular weight 4800), then compression molded into a ring shape with an outer diameter of φ20 mm, an inner diameter of φ18 mm, and a height of h7 mm, and then cured in air at 150 ° C. for 30 minutes. Nd—Fe—B based compression bonded magnet A (ring magnet) was obtained.

"Manufacture of bonded magnet B"
After adjusting the magnetic powder by the same method as described above, coupling treatment, and mixing this with bisphenol A type epoxy resin (number average molecular weight 2400), compression molding to an outer diameter of 20 mm, an inner diameter of 18 mm, and a height of h7 mm Then, it was cured in air at 150 ° C. for 30 minutes to obtain an Nd—Fe—B-based compression bonded magnet B (ring magnet).

<Example 1>
Cationic electrodeposition coating was performed on the Nd—Fe—B-based compression bonded magnet A obtained above using INSULEED3030BL manufactured by Nippon Paint Co., Ltd. as a cationic electrodeposition coating.
Here, the above electrodeposition paint is obtained by reacting propagyl alcohol and sulfide with a glycidyl functional group of a cresol novolac type epoxy resin and diluting to a specific concentration with deionized water. Acetonate and monoethanolamine were added, the mixture was stirred with a high-speed mixer, and deionized water was further added to adjust to a predetermined solid content concentration.

The temperature of the bath containing the coating liquid is adjusted to 30 ° C., and the bonded magnet A obtained above is held on the outer peripheral surface by the cathode member 212 as shown in FIG. 3, and is immersed in the bath. A voltage was applied to perform cationic electrodeposition coating.
In this cationic electrodeposition coating, the voltage was increased to 300 V in 5 seconds after the voltage application, and then the voltage was maintained at 300 V for 175 seconds to perform cationic electrodeposition coating.

After coating, wash with water, bake at 180 ° C. for 20 minutes, and after air cooling, measure the volume resistivity of the coating (that is, the value of volume resistivity of the present invention is after baking) and evaluate the electrode trace protrusion coefficient ε value went.
Here, TAKEDA RIKEN TR-8601 HIGH MEGOHM METER was used to measure the volume resistivity of the coating, and the above bonded magnet formed by electrodeposition coating with a coating thickness of 20 μm at a bath temperature of 23 ° C. conforms to JIS K 7194. I went.

The evaluation of the electrode trace (cathode member trace) projection coefficient ε value was performed by the method shown in FIG.
Specifically, the electrode trace protrusion coefficient ε was determined as ε = Δ1 / Δ0 when the film thickness of the coating a was Δ0 and the protrusion height of the protrusion b was Δ1.
In FIG. 1, 208 denotes a ring magnet.

In addition to these evaluations, the pencil hardness of the coating after baking treatment and the film thickness difference between the film thickness of the inner peripheral surface and the film thickness of the outer peripheral surface of the ring magnet were also evaluated.
Here, the pencil hardness and film thickness of the coating were measured and evaluated as follows.
(A) Evaluation of pencil hardness of the coating The test was conducted in accordance with JIS K 7194. When the coating was scratched sequentially from the soft pencil of the core, and the coating was scratched, Hardness ".
(B) Evaluation of coating film thickness difference Electrodeposited magnets are embedded in epoxy resin and cured, then cut with diamond cutters at desired positions, and then polished to a mirror finish The film thickness was measured by SEM.
These results are shown in Table 1.

<Comparative Example 1>
A commercially available cationic electrodeposition coating was used as the electrodeposition coating, and the above-described bonded magnet B was subjected to cationic electrodeposition coating, and various evaluations were performed in the same manner as described above.
Here, the following electrodeposition paints were used.
Diphenylmethane diisocyanate blocked with ethylene glycol mono-2-ethylhexyl ether was mixed in a predetermined ratio with a resin solution obtained by reacting bisphenol A type epoxy resin and diethanolamine, and this was used as an electrodeposition paint. Add 1383 g of this paint to an aqueous solution of 21 g of acetic acid in 672 g of deionized water prepared in advance, stir for 1 hour with a high-speed rotary mixer, and then add 4844 g of deionized water to adjust the solid content concentration to 15% by mass. This was used as an electrodeposition solution.
The results are shown in Table 1.

As is apparent from the results in Table 1, the volume resistivity of the electrodeposition coating film is set to a high resistance of 1.6 × 10 ¹⁷ Ω · cm of 5 × 10 ¹⁵ Ω · cm or more according to the present invention. It can be seen that the protruding height of the portion b can be effectively reduced and the difference in film thickness between the outer peripheral surface and the inner peripheral surface of the ring magnet can be reduced.

  Although the embodiment of the present invention has been described in detail above, this is merely an example, and the present invention can be configured in various forms without departing from the spirit of the present invention.

It is explanatory drawing of the evaluation method of the projection part used by embodiment of this invention. It is the figure which showed the conventionally well-known thing as an example of use of a ring magnet. It is the figure which showed the principal part of the method of the cation electrodeposition coating of a ring magnet. It is explanatory drawing of the malfunction which has arisen conventionally. It is explanatory drawing of the malfunction different from having shown in FIG. It is explanatory drawing which showed the principal part of the method of the cation electrodeposition coating of a stator core with the malfunction which generate | occur | produces.

Claims (1)

An electrodeposition coating part for a motor, characterized in that the surface has been subjected to cationic electrodeposition coating, and the volume resistivity of the coating film is 5 × 10 ¹⁵ Ω · cm or more at a temperature of 23 ° C.

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