JP4416558B2 - Motor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a motor such as a small stepping motor and a manufacturing method thereof.

  A conventional small cylindrical stepping motor is shown in FIG. 5 (see, for example, FIG. 6 of Patent Document 2).

  A coil 105 is concentrically wound around the bobbin 101, and the bobbin 101 is sandwiched and fixed in the axial direction by two yokes 106. The yoke 106 has magnetic pole teeth 106a along the circumferential direction of the inner surface of the bobbin 101. 106b are alternately arranged, and the yoke 103 integral with the magnetic pole teeth 106a and 106b is fixed to the case 103 to constitute the stator yoke 102. A flange 115 and a bearing 108 are fixed to one of the two sets of cases 103, and another bearing 108 is fixed to the other case 103. The rotor 109 is composed of a rotor magnet 111 fixed to the rotor shaft 110, and the rotor shaft 110 is rotatably supported between two bearings 108.

  In addition, a stepping motor having the structure shown in FIGS. 3 and 4 suitable for reducing the size and increasing the torque of the stepping motor has been proposed. The stepping motor includes a cylindrical rotor magnet 11 having an output shaft that is alternately magnetized to n magnetic poles in the circumferential direction and that is rotatably supported by inner yokes 14 and 15 described later, and the rotor magnet 11. The outer yokes 12 and 13 are yokes made of a soft magnetic material and are opposed to each other in the axial direction with the coil interposed therebetween, the inner yokes 14 and 15 are yokes made of a soft magnetic material, the inner yokes 14 and 15 and the outer yoke. The coils 16 and 17 for exciting the coils 12 and 13; the coil bobbins 18 and 19 for supporting the coils 16 and 17; the motor cover 20 for supporting the outer yokes 12 and 13; The bearings 21 and 22 are fitted to the inner diameters of 14 and 15.

  As a material constituting the yoke of the conventional stepping motor, electromagnetic soft iron (SUY) and cold rolled steel plate (SPC), which are steel plate materials generally having a carbon content of 0.02% by mass or less, are used. . SUY and SPC have good direct-current magnetic characteristics, but poor alternating-current magnetic characteristics during motor rotation. This is because an eddy current is likely to be generated because the electrical resistivity is low, and the influence becomes greater as the drive frequency becomes higher. Therefore, proposals have been made using a nickel-iron alloy (permalloy) plate or sendust alloy plate as the material of the yoke (see, for example, Patent Document 3 and Patent Document 4).

In general, the yoke is formed into a shape by machining such as pressing, punching, and bending of a plate material. After producing the shape, 700 ° C. to 900 ° C. (for example, refer to Patent Document 1) in vacuum or in a reducing atmosphere in order to remove the processing strain when forming the plate and the processing strain when forming the shape such as a press. In the case of permalloy, heating is performed at 1000 ° C. or higher. In general, electroless nickel plating or electrolytic nickel plating is applied as a rust prevention treatment.
Japanese Patent No. 3061820 JP 2000-217333 A Japanese Patent Laid-Open No. 10-14204 JP 2002-320372 A

  As described above, the conventional yoke is generally formed by pressing a plate material, but the SUY plate, the SPC plate, and the nickel-iron alloy plate of Patent Document 3 require heat treatment to remove strain. . However, the heat treatment makes it extremely soft. As seen in the yoke 106 in FIG. 5 and the outer yokes 12 and 13 in FIG. 3 and FIG. 4, the magnetic pole portion at the tip of the stator yoke has a comb-like shape, so that it is soft and easily deformed during assembly. When the yoke is deformed, the gap between the rotor magnet and the comb-shaped magnetic pole portion is not uniform, resulting in a small torque and an incorrect step angle. In severe cases, it may not rotate due to contact. That is, it greatly affects the manufacturing yield.

  On the other hand, when Sendust alloy is used for the yoke as in Patent Document 4, since it is hard and brittle, cracks are likely to occur during press working. As for press working, it is expected that high dimensional accuracy and downsizing become more difficult as the motors become smaller regardless of the material. Further, the inner yokes 14 and 15 of FIGS. 3 and 4 are manufactured by cutting a round bar or forging a plate material. However, the processing becomes difficult as the size is reduced.

(Object of invention)
An object of the present invention is to provide a motor capable of achieving an improvement in driving torque and improving a manufacturing yield with a high dimensional accuracy by improving an AC magnetic characteristic and mechanical strength of a yoke, and a manufacturing method thereof. Is

  In order to achieve the above object, the present invention according to claim 1 is a motor including a yoke as a magnetic circuit excited by a coil, wherein the yoke includes nickel-iron containing sulfur formed by electroplating. It is made of an alloy, and the nickel-iron alloy has an iron content of 35 to 59% by mass and a sulfur content of 0.002 to 0.12% by mass.

  According to a second aspect of the present invention, there is provided a rotor magnet in which an output shaft is rotatably supported, a yoke having a magnetic pole portion facing the rotor magnet and facing the gap, and constituting a magnetic circuit, In a motor provided with a coil for exciting a yoke, the yoke is made of a nickel-iron alloy containing sulfur formed by electroplating, and the iron content of the nickel-iron alloy is 35 to 59% by mass, And the content rate of sulfur is 0.002-0.12 mass%, It is characterized by the above-mentioned.

  According to a third aspect of the present invention, there is provided a cylindrical rotor magnet that is magnetized by a plurality of magnetic poles and is rotatably supported, and a plurality of rotor magnets facing the outer diameter side and the outer gap of the rotor magnet. An outer yoke having a magnetic pole part, a magnetic pole part facing the inner gap and the inner gap of the rotor magnet, and an inner yoke constituting a magnetic circuit together with the outer yoke, and wound around the inner yoke In the motor including the outer yoke and the coil for exciting the inner yoke, at least one of the outer yoke and the inner yoke is made of a nickel-iron alloy containing sulfur formed by electroplating, and the nickel-iron The iron content of the alloy is 35 to 59% by mass, and the sulfur content is 0.002 to 0.12% by mass.

According to a fourth aspect of the present invention, when the motor according to any one of the first to third aspects is manufactured, a non-recessed portion having the same shape as the yoke is formed on a mold made of a conductive material. By forming a conductive material, a recess having the same shape as the yoke is exposed on the surface of the mold, and the recess of the mold is immersed in a plating bath for depositing a nickel-iron alloy containing sulfur. Thereafter, the mold is energized as a cathode, a nickel-iron alloy containing sulfur is deposited in the recess, an electroformed yoke having an arbitrary thickness is formed, the electroformed yoke is removed from the recess, and the electroformed yoke is removed. It is characterized by obtaining.

  According to the present invention, by improving the AC magnetic characteristics and mechanical strength of the yoke, the drive torque can be improved, and the manufacturing yield can be increased with high dimensional accuracy.

  In the motor according to the present invention, the yoke, for example, the outer yokes 12 and 13 shown in FIGS. 3 and 4, the inner yokes 14 and 15, and the yoke 106 shown in FIG. It consists of an iron alloy, and the nickel content of this nickel-iron alloy is 35 to 59% by mass, and the sulfur content is 0.002 to 0.12% by mass ( A member produced by electroplating is hereinafter referred to as electroforming).

  When the iron content in the nickel-iron alloy is 35 to 59 mass% and the sulfur content is 0.002 mass% or more, the magnetic flux density is 1.4 T or more and the coercive force is 1 Oe or less, Further, since the electrical resistivity is 25 to 50 μΩ · cm, which is 2 to 5 times that of SUY and SPC, it has a high driving torque in a wide frequency range from a low frequency to a high frequency. When the iron content is less than 35% by mass or more than 59% by mass, the magnetic flux density decreases rapidly, so that the torque is also smaller than that of a motor composed of a yoke made of SUY or SPC material. Furthermore, it was found that when the sulfur content was 0.002% by mass or more, it was hard and hardly deformed. If it is less than 0.002% by mass, it is difficult to form as a plating film, and it is not a hard film. On the other hand, if the amount of sulfur exceeds 0.12% by mass, it becomes too hard and cracks are likely to occur during electroforming. Therefore, the sulfur content is preferably 0.12% by mass or less. This high magnetic flux density and hard properties are characteristics after electroforming. The content of nickel and iron and the content of sulfur are unique properties that determine the magnetic properties and hardness.

  When the composition of the plating bath is, for example, as shown in FIG. 6, nickel sulfate, boric acid, sodium chloride, sodium lauryl sulfate, ferrous sulfate, sodium saccharin, the iron content is nickel sulfate and ferrous sulfate. It is determined by controlling the amount of addition, current density, and plating bath temperature. Sulfur is contained in nickel sulfate, sodium lauryl sulfate, ferrous sulfate, and saccharin sodium, and the content is determined by controlling the amount of ferrous sulfate and sodium saccharin added, the current density, and the plating bath temperature.

  Industrially produced permalloy plates do not show good magnetic properties without heat treatment, but the electroformed nickel-iron alloy yoke according to the present invention does not require heat treatment, and is greatly different in this respect.

  The point is to appropriately determine the iron content and the sulfur content, but it is easy to control because it is electroformed. However, depending on the shape of the electroformed product, a heat treatment for removing distortion during plating may be performed. The heating temperature is preferably 350 ° C. or lower. When heated at a temperature exceeding 350 ° C., it tends to become brittle.

  In addition, since the rust tends to be generated when the amount of iron is large, when the environment to be used is high temperature and high humidity, it is only necessary to apply rust prevention plating such as electroless nickel or electrolytic nickel on the electroformed product. Since the anticorrosive film only needs to be 2 to 5 μm, it does not affect the magnetic properties and hardness of the electroformed product. The use of the yoke 106 in FIG. 5 and the outer yokes 12 and 13 and the inner yokes 14 and 15 in FIGS. 3 and 4 can improve the driving torque characteristics, and there is no deformation at the time of assembly. Yield is high.

  Next, a method for manufacturing the electroformed yoke will be described with reference to FIGS. First, a method of manufacturing the outer yoke 12 (13 has the same shape as 12) shown in FIGS. 3 and 4 will be described with reference to FIGS. When the outer yoke 12 shown in FIGS. 3 and 4 is manufactured, it is manufactured by cutting from a block of a metal material or plastic material having good cutting properties at the tip of a die 30 made of a conductive material having the same outer diameter as the inner side of the outer yoke 12. The master die 31 of the outer yoke 12 is fitted (a, b). Then, a non-conductive substance 32 such as an ultraviolet curable resin is formed on the surface portion of the die 30 other than the portion where the master die 31 is fitted by coating or the like. The non-conductive material 32 may be thicker than the outer yoke 12. After the non-conductive substance 32 is cured by irradiating ultraviolet rays or the like, the master mold 31 is removed from the mold 30 (c). As a result, a recess is formed at a location on the mold 30 where the master mold 31 was located. This completes the mother die 33 for plating.

  This matrix 33 is immersed in a plating bath 34 for depositing a nickel-iron alloy. The mother die 33 is used as a cathode, and the bag 35 containing a nickel chip is used as an anode. The matrix 33 is rotated in order to deposit a uniform film thickness. Energization is performed to deposit a nickel-iron alloy only on the portion of the master die 33 where the master die 31 is removed. The energization is performed until the deposited film has a required thickness (d).

  When the required thickness is reached (e), the matrix 33 is pulled out by hand, for example, and removed to obtain an electroformed product of the outer yoke 12 (f). Further, the yoke 106 of the motor shown in FIG.

  Since the outer yoke 12 is cylindrical, the mold 30 in this case is preferably a cylindrical rod having a diameter slightly larger than the inner diameter of the outer yoke 12. For the cylindrical rod 30 made of a conductive material, for example, stainless steel, brass, or phosphor bronze is preferably used as it is, or a surface of which is coated with a coating that hardly dissolves in acid or alkali such as hard chrome. Moreover, in order to make it easy to pull out the electroformed product from the mother die 33, a peeling layer may be applied to the mother die 33 before plating. The master mold 31 may be manufactured by cutting, casting, die casting, or thermoplastic resin injection molding. As the material, a metal having good cutting properties such as stainless steel, brass, phosphor bronze, aluminum and copper may be used. The plastic material may be a general resin such as an epoxy resin, a phenol resin, an amino resin, an unsaturated polyester resin, or a silicone resin, which is a thermosetting resin. In the case of injection molding, a thermoplastic resin such as POM, ABS, or PPS may be used.

  Next, the case of the inner yoke 14 (15 is the same shape as 14) in FIGS. 3 and 4 will be described with reference to FIGS. The tip portion 41 of the mother die 40 is made as a recess in the same shape as the inner shape of the inner yoke 14 by cutting or the like (a). A non-conductive material 32 is provided from the end face of the tip 41 above the same height Y as the length of the inner yoke 14 in the same manner as the electroformed outer yoke 12 (b). The non-conductive material 32 may be provided thicker than the inner yoke 14. Thereafter, like the electroformed outer yoke 12, the mother die 40 is immersed in a plating bath 34 for depositing a nickel-iron alloy and is energized (c). When the required thickness is reached (d), the matrix 40 is pulled out by hand, for example, and removed to obtain an electroformed product of the inner yoke 14 (e). Since the film thickness of the electroformed product is determined by the energization time, the dimensional accuracy is extremely high.

  As a plating bath, a sulfate bath, a sulfamate bath, and a chloride bath by electroplating are easy to produce nickel-iron alloy plating. A pit inhibitor, a brightener, a pH adjuster, or the like may be appropriately added to these plating baths. As the plating bath, the above-described sulfate bath is preferable because the ratio of nickel and iron and the amount of sulfur added can be easily controlled. Although the thickness of the electroformed yoke depends on the motor specifications, it is easy to manage by the energization time.

  Hereinafter, the present invention will be described in more detail with reference to examples.

<Motor evaluation>
About Examples 1-5 shown by FIG. 6, it evaluated by experiment.

<Experiment 1>
The effectiveness of the outer yokes 12 and 13 made of an electroformed nickel-iron alloy containing sulfur was examined. Referring to FIG. 1, a master die 31 of the outer yoke 12 shown in FIGS. 3 and 4 obtained by cutting a phosphor bronze block is fitted to a die 30 made of a cylindrical stainless steel rod having an outer diameter Φ6. The non-conductive substance 32 was formed by applying an ultraviolet curable resin to the exposed portion of the mold 30 with a thickness of 500 μm and irradiating it with ultraviolet rays to cure. When the master die 31 is removed from the mother die 33, a recess is formed at a location on the die 30 where the master die 31 was located. This mother die 33 is immersed in a nickel-iron plating bath 34 containing sulfur of the plating conditions of Examples 1 to 5 in FIG. 6, energized while rotating at 20 rpm using the mother die 33 as a cathode, and electrolyzed, with a thickness of 300 μm. The outer yoke 12 made of the electroformed nickel-iron alloy was prepared and removed from the mother die 33. The temperature of the plating bath was 50 ± 1 ° C. On the other hand, the inner yokes 14 and 15 were produced by cutting a SUY bar. Thereafter, heat treatment was performed at 850 ° C. for 2 hours, and electroless nickel plating was applied to 3 μm for rust prevention treatment. The inner yokes 14 and 15 made of the SUY material were press-fitted into the outer yokes 12 and 13 made of an electroformed nickel-iron alloy to produce a stator yoke. Incorporated in the motors of FIGS. 3 and 4, the drive frequency-pullout torque was evaluated.

  As a reference product, a 300 μm thick SUY plate was pressed to produce the outer yokes 12 and 13 that were subjected to the same heat treatment and rust-proof plating as the inner yokes 14 and 15. The stator yoke combined with was incorporated into the motor of FIGS. 3 and 4 and the drive torque was evaluated. The results are shown in FIG. 7 (relative values with a torque of 500 PPS as 1). The torque was found to be higher at all frequencies in the stator yoke in which the outer yoke made of electroformed nickel-iron alloy and the inner yoke made of SUY were combined.

<Experiment 2>
Next, the effectiveness of the inner yokes 14 and 15 made of an electroformed nickel-iron alloy was examined. Referring to FIG. 2, a tip 41 having the same shape as the inner shape of the inner yokes 14 and 15 in FIGS. 3 and 4 is cut at the tip of a mother die 40 made of a cylindrical stainless rod having an outer diameter of Φ4.5. It was made with. Next, a non-conductive substance 32 was formed by applying 500 μm of ultraviolet curable resin from the end face of the tip 41 above the position of the same Y as the height of the inner yokes 14, 15 and curing it by irradiating with ultraviolet rays. 6 is immersed in a nickel-iron plating bath having the plating conditions of Examples 1 to 5 in FIG. 6, energized while rotating at 20 rpm using the mother die 40 as a cathode, electrolyzed, and electroformed nickel having a thickness of 300 μm. -Inner yokes 14 and 15 made of an iron alloy were produced. The inner yokes 14 and 15 made of electroformed nickel-iron alloy were press-fitted into the outer yokes 12 and 13 made of SUY produced in Experiment 1 to produce a stator yoke. Incorporated in the motors of FIGS. 3 and 4, the drive frequency-pullout torque was evaluated. As a reference product, a comparison was made with a motor in which an outer yoke made of SUY evaluated in Experiment 1 and an inner yoke were combined. The result is shown in FIG. The torque was found to be higher at all frequencies in the stator yoke in which the inner yoke made of electroformed nickel-iron alloy and the outer yoke made of SUY were combined.

<Experiment 3>
3 and 4 show a stator yoke by combining the outer yokes 12 and 13 made of the electrocast nickel-iron alloy of Examples 1 to 5 and the inner yokes 14 and 15 obtained in Experiments 1 and 2 above. Built into the motor. Then, the motors of the outer yoke made of SUY and the inner yoke, which are reference products, and the driving torque were compared and evaluated. The result is shown in FIG. The torque was found to be high at all frequencies in a motor with a combination of an outer yoke and an inner yoke made of an electroformed nickel-iron alloy. Further, this combination of electroformed yokes showed the highest torque as compared with Experiments 1 and 2.

(Comparative Examples 1-6)
In the same procedure as in Experiment 3 of Examples 1 to 5, a stator yoke having a combination of an electroformed outer yoke and an inner yoke of Comparative Examples 1 to 3 and 6 of FIG. Built and evaluated. The result is shown in FIG. It was found that the motor, which is a reference product combining the outer yoke and the inner yoke made of SUY material, has higher torque at all frequencies than the motors manufactured in Comparative Examples 1 to 3 and 6 in FIG. Moreover, the comparative example 4 peeled off from the mother die during plating, and the shape could not be formed well. In Comparative Example 5, the yoke that can be evaluated could not be produced because it cracks when removed from the mother die.

<Evaluation of magnetic properties>
FIG. 6 shows the values of magnetic flux density and coercive force when an iron mass% of an electroformed nickel-iron alloy and a magnetic field of 10 Oe are applied. As a result of evaluation by incorporating a yoke made of an electroformed nickel-iron alloy into a motor, when the magnetic flux density is 1.4 T or more like a yoke having an iron content of 35 to 59% by mass, a yoke made of SUY It was found that the characteristics were better than the motor used. Moreover, the yoke made of SUY was heat-treated, and the Vickers hardness (Hv 100 g) of the surface of the electroless nickel-plated rust preventive treatment was measured, but it was very soft at Hv 90. On the other hand, when the Hv of the yoke having a motor content of 35 to 59% by mass with a large motor torque is 400 or more, the yoke is more than five times harder than the yoke made of SUY, and therefore, it is difficult to deform.

  The present invention can be applied not only to a stepping motor but also to other DC motors and AC motors.

It is a figure which shows the manufacturing method of the electroformed outer yoke by this invention. It is a figure which shows the manufacturing method of the electroformed inner yoke by this invention. It is sectional drawing which shows the structural example of the motor common to a prior art example and this invention. FIG. 4 is an exploded perspective view of the motor shown in FIG. 3. It is sectional drawing which shows the other structural example of the motor common to a prior art example and this invention. It is a figure which shows the Example and comparative example of this invention. It is a figure which shows the drive frequency-pullout torque characteristic in Experiment 1 of the Example of this invention. It is a figure which shows the drive frequency-pullout torque characteristic in Experiment 2 of the Example of this invention. It is a figure which shows the drive frequency-pullout torque characteristic in Experiment 3 of the Example of this invention. It is a figure which shows the drive frequency-pullout torque characteristic of the comparative example with respect to the Example of this invention.

Explanation of symbols

11 Rotor magnet 12, 13 Outer yoke 14, 15 Inner yoke 16, 17 Coil 18, 19 Coil bobbin 20 Motor cover 21, 22 Bearing 30 mold 31 Master mold 32 Non-conductive material 33 Mold 34 Plating bath 35 Anode 36 Power supply 40 Mother mold 41 Tip 101 Bobbin 102 Stator yoke 103 Case 105 Coil 106 Yoke 106a, 106b Magnetic pole teeth 108 Bearing 109 Rotor 110 Rotor shaft 111 Rotor magnet 115 Flange

Claims (4)

In a motor having a yoke as a magnetic circuit excited by a coil,
The yoke is made of a nickel-iron alloy containing sulfur formed by an electroplating method. The nickel-iron alloy has an iron content of 35 to 59% by mass and a sulfur content of 0.002 to 0. A motor characterized by being 12% by mass. In a motor provided with a rotor magnet whose output shaft is rotatably supported, a yoke having a magnetic pole part facing the rotor magnet and facing the gap, and a coil for exciting the yoke,
The yoke is made of a nickel-iron alloy containing sulfur formed by an electroplating method. The nickel-iron alloy has an iron content of 35 to 59% by mass and a sulfur content of 0.002 to 0. A motor characterized by being 12% by mass. A cylindrical rotor magnet that is magnetized by a plurality of magnetic poles and is rotatably supported, an outer yoke having a plurality of magnetic pole portions facing the outer diameter side and the outer gap of the rotor magnet, and the rotor magnet An inner yoke that forms a magnetic circuit together with the outer yoke, and a coil that is wound around the inner yoke and that excites the outer yoke and the inner yoke. In a motor with
At least one of the outer yoke and the inner yoke is made of a nickel-iron alloy containing sulfur formed by electroplating, the iron content of the nickel-iron alloy is 35 to 59% by mass, and the sulfur content A motor having a rate of 0.002 to 0.12% by mass. When manufacturing the motor according to any one of claims 1 to 3 , a surface of the mold is formed by forming a non-conductive substance on the mold made of a conductive material except for a recess having the same shape as the yoke. A recess having the same shape as that of the yoke is exposed, and the recess of the mold is immersed in a plating bath for depositing a nickel-iron alloy containing sulfur. A method of manufacturing a motor, wherein a nickel-iron alloy containing sulfur is deposited at a place to form an electroformed yoke of an arbitrary thickness, and the electroformed yoke is obtained by removing the electroformed yoke from the recess.

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