JP4657635B2 - motor - Google Patents

Description

  The present invention relates to a motor such as a small stepping motor.

  A conventional small cylindrical stepping motor is shown in FIG. 4 (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 output shaft 110, and the output shaft 110 is rotatably supported between two bearings 108.

  Further, there has been proposed a stepping motor having the structure of FIGS. 2 and 3 suitable for downsizing and increasing the torque of the stepping motor. This stepping motor includes a cylindrical rotor magnet 11 having an output shaft 23 magnetized by n poles in the circumferential direction, outer yokes 12 and 13 disposed opposite to each other in the thrust direction with the rotor magnet 11 interposed therebetween. Inner yokes 14 and 15, coils 16 and 17 that excite the inner yokes 14 and 15 and outer yokes 12 and 13, coil bobbins 18 and 19 that support the coils 16 and 17, and motor covers that support the outer yokes 12 and 13 20 and bearings 21 and 22 which are made of a mold or a copper-based nonmagnetic material and are fitted to the inner diameters of the inner yokes 14 and 15.

  As a material constituting the yoke of the conventional stepping motor, electromagnetic soft iron (SUY), which is generally a steel plate material having a low carbon content, for example, a carbon content of 0.05% by mass or less, a cold rolled steel plate (SPC) ) Is used. Further, a sintered member using the above SUY or SPC iron powder is used. SUY and SPC have good direct-current magnetic characteristics, but poor alternating-current magnetic characteristics during motor rotation. This is because the electrical resistivity is low and eddy currents are likely to be generated, and the influence increases as the drive frequency increases. 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 forming the shape, 700 to 900 ° C. (for example, refer to Patent Document 1), permalloy 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 heating at 1000 ° C. or higher. In general, electroless nickel plating or electrolytic nickel plating is applied as a rust prevention treatment. On the other hand, the output shaft is manufactured by cutting a stainless steel bar, a brass bar, a phosphor bronze bar, and a free-cutting iron bar. Brass, phosphor bronze, and free-cutting iron have good workability compared to stainless steel rods, so the cost is low, but rust is likely to occur. For this reason, electroless nickel plating or electrolytic nickel plating is applied to the rust preventive treatment in the same manner as the stator yoke. The bearing is generally a sintered material impregnated with a mold, copper-based or iron-based lubricating oil.
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 can be seen from the yoke 106 in FIG. 4 and the outer yokes 12 and 13 in FIG. 2 and FIG. 3, the magnetic pole portion at the tip of the stator yoke has a comb-like shape, and 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, a rotor magnet is provided on the output shaft. As a method of providing a rotor magnet on the output shaft, press the rotor magnet into the output shaft, join with an adhesive, or if the rotor magnet is a plastic magnet that can be processed by injection molding, insert the output shaft into the injection molding. After that, it is made by so-called insert molding. However, since the diameter of the output shaft becomes smaller with the miniaturization of the motor, the output shaft is likely to be deformed during the production as described above.

  Further, since the motor torque is reduced with the miniaturization of the motor, it is necessary to reduce the friction at the time of contact with the bearing.

(Object of invention)
The first object of the present invention is to provide a motor that can improve the drive torque and improve the manufacturing yield with high dimensional accuracy by improving the AC magnetic characteristics and mechanical strength of the yoke. To do.

  The second object of the present invention is to provide a motor that can improve the strength of the output shaft and enhance the wear resistance, thereby achieving high durability.

In order to achieve the first object, the present invention according to claim 1 is a motor including a yoke made of an iron material as a magnetic circuit excited by a coil, and the surface of the yoke includes nickel containing sulfur. -It is set as the motor which consists of an iron alloy and formed the plating film whose content rate of iron is 3-60 mass% and whose content rate of sulfur is 0.002-0.12 mass% more than 20 micrometers .

Similarly, in order to achieve the first object, the present invention according to claim 2 includes a rotor magnet fixed to a rotating shaft that is rotatably supported, and a magnetic pole facing the rotor magnet with a gap therebetween. In a motor having a yoke made of an iron material that constitutes a magnetic circuit and a coil that excites the yoke, the surface of the yoke is made of a nickel-iron alloy containing sulfur and has an iron content of 3 to 60 mass. % in, and in which the content of sulfur is the motor that the plating film is formed above 20μm is from .002 to .12% by weight.

In order to achieve the second object, the present invention according to claim 3 includes a rotor magnet fixed to a rotating shaft that is rotatably supported, and a magnetic pole facing the rotor magnet with a gap therebetween. And a coil for exciting the yoke, and a surface of the output shaft made of a nickel-iron alloy containing sulfur and having an iron content of 3 to 60% by mass. In addition, a motor in which a plating film having a sulfur content of 0.002 to 0.12% by mass is formed by 5 μm or more is used.

According to the first or second aspect of 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. A motor can be provided.

According to the third aspect of the present invention, it is possible to provide a motor capable of improving the strength of the output shaft and enhancing the wear resistance to enhance the durability.

  The motor according to the present invention is first characterized in that a nickel-iron alloy containing sulfur is plated on the yoke. As composition of nickel-iron alloy plating containing sulfur, it is preferable that the content rate of iron is 3-60 mass%, and the content rate of sulfur is 0.002-0.12 mass%. It was found that the above composition had a characteristic of an electric resistivity of 20 to 60 μΩ · cm, which is 2 to 5 times that of SUY and SPC, and a Vickers hardness Hv (load 100 g) of 400 or more. Therefore, the eddy current loss at a high frequency is smaller than that of the iron material used in the conventional motor, and it has a hard property.

  In the case of an iron material having a low carbon content, the saturation magnetic flux density (hereinafter referred to as Bs) is 2T or more, but when the iron content of the nickel-iron alloy is 3 to 60% by mass, Bs is 0.8T to 1%. .6T, and Bs is smaller than iron materials having a low carbon content. Therefore, taking advantage of the large Bs that is the merit of the iron material and the high electrical resistivity of the nickel-iron alloy, nickel-iron alloy plating is applied to the surface of the yoke made of the iron material, so that the low drive frequency is changed to the high drive frequency. A motor having a high driving torque in a wide driving frequency band up to can be obtained.

  Furthermore, it turned out that it is hard and it is hard to deform | transform when the content rate of sulfur is 0.002 mass% or more. 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 sulfur content exceeds 0.12% by mass, it becomes too hard and cracks are likely to occur during plating. Therefore, the content of sulfur is preferably 0.002 to 0.12% by mass. It possesses high electrical resistivity and is a hard property, which is a unique property in which the iron content and sulfur content determine the magnetic properties, electrical resistivity and hardness. However, if the amount of iron is large, rust is likely to occur. Therefore, if the environment used is high temperature and high humidity, nickel-iron alloy plating with less iron on top of nickel-iron alloy plating, electroless nickel, Applying anti-corrosion plating such as electrolytic nickel. As the plating thickness increases, the magnetic properties and electrical resistivity of the nickel-iron alloy dominate, but the high Bs properties of iron decrease. What is necessary is just to select thickness and the content rate of iron according to the structure of a motor. The use of the yoke 106 in FIG. 4, the outer yokes 12 and 13, and the inner yokes 14 and 15 in FIGS. 2 and 3 can improve the driving torque characteristics, and since it is hard, it prevents deformation when assembled. In addition, the production yield is high.

  Second, it is characterized by plating a nickel-iron alloy containing sulfur on the output shaft. As explained above, the nickel-iron alloy plating film has hard characteristics. Since the diameter of the output shaft is reduced with the miniaturization of the motor, the output shaft is easily deformed when assembled to the rotor magnet. Therefore, deformation can be prevented by processing a stainless steel rod, brass rod, phosphor bronze rod, and free-cutting iron rod into a shape as a predetermined output shaft, followed by nickel-iron alloy plating. Further, since the motor torque is reduced with the miniaturization of the motor, it is necessary to reduce the friction when the output shaft and the bearing come into contact with each other. However, the nickel-iron alloy plating of the present invention is not only hard, but also has high wear resistance because of its low coefficient of friction. The plating thickness is preferably thick in order to improve the strength of the output shaft. For example, in the case of brass as an output shaft base material, it is easy to rust.

  Next, regarding the method for producing a nickel-iron alloy plating film of the present invention, as a plating bath, a sulfate bath, a sulfamate bath, and a chloride bath by electroplating are easy to produce a 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 that can easily control the ratio of nickel to iron and the amount of sulfur added is preferable. The plating thickness depends on the motor specifications, but can be easily controlled because it is determined by the energization time.

  When the composition of the plating bath is nickel sulfate, boric acid, sodium chloride, sodium lauryl sulfate, ferrous sulfate, sodium saccharin as shown in FIG. 5, for example, 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.

  Hereinafter, the present invention will be described in detail using examples.

<Motor evaluation>
About Example 1-Example 7 shown by FIG. 5, it evaluated by experiment.

<Experiment 1>
The effectiveness of plating a nickel-iron alloy on the outer yoke 12 shown in FIGS. 2 and 3 (13 has the same shape as 12) produced by press working from a SUY plate was examined. The outer yoke 12 was shaped by pressing from a SUY plate having a thickness of 260 μm. Thereafter, heat treatment was performed in vacuum at 850 ° C. for 2 hours. In order to plate the outer yoke 12 with a nickel-iron alloy, as shown in FIG. 1, the outer yoke 12 is put in a stainless steel rod 30 having a mesh that does not drop the parts. At the same time, an electrode of a cathode 33 made of stainless steel, for example, is also inserted. The gutter 30 is immersed in a nickel-iron alloy plating solution 31. An anode 32 made of nickel is immersed in a nickel-iron alloy plating solution 31.

  In the above state, electricity is applied while rotating the collar 30, and the outer yoke 12 is plated with a nickel-iron alloy. This plating method is called barrel plating, which is a general electroplating method. When the required plating thickness was reached, the energization was stopped, and the outer yoke 12 was taken out from the trough 30 to obtain the outer yoke 12 plated with nickel-iron alloy. Plating is performed under the plating conditions of Examples 1 to 7 in FIG. The plating thickness was approximately 20 μm. The thickness of the outer yoke 12 including plating is approximately 300 μm. The temperature of the plating bath was 50 ± 1 ° C. On the other hand, the inner yoke 14 (15 has the same shape as 14) was produced by cutting a SUY rod. 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 plated with nickel-iron alloy to produce a stator yoke. It is incorporated in the motor shown in FIGS. 2 and 3 and the drive frequency-pullout torque is evaluated. As a reference, a plate material made of SUY having a thickness of 300 μm was pressed, and electroless nickel plating was applied by 3 μm for the same heat treatment and rust prevention treatment as the above inner yoke. A stator yoke composed of a SUY outer yoke and an inner yoke was assembled into the motor shown in FIG. 3, and the driving torque was evaluated. The result is shown in FIG. 6 (relative value 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 plated with the nickel-iron alloy of Examples 1 to 7 and the inner yoke made of SUY were combined. Examples 1 to 7 showed substantially the same driving torque.

<Experiment 2>
Next, the effectiveness when the nickel-iron alloy was plated on the inner yoke 14 (14 has the same shape as 15) of FIGS. After cutting the inner yoke of FIG. 3 having a basic thickness of 260 μm from the SUY rod, heat treatment was performed at 850 ° C. in vacuum for 2 hours. Among them, in order to plate the nickel-iron alloy on the yoke, as in Experiment 1, the inner yoke 14 was placed in the trough 30 of FIG. 1 and plated with a nickel-iron alloy. Plating was performed under the plating conditions of Examples 1 to 7 in FIG. The plating thickness was approximately 20 μm. The thickness of the inner yoke including plating is approximately 300 μm. The temperature of the plating bath was 50 ± 1 ° C. On the other hand, the outer yokes 12 and 13 were produced by pressing a plate material made of 300 μm thick SUY, followed by heat treatment at 850 ° C. for 2 hours, and applying electroless nickel plating for 3 μm for rust prevention treatment. . Inner yokes 14 and 15 plated with nickel-iron alloy were press-fitted into the outer yokes 12 and 13 made of the SUY material to produce a stator yoke. The drive frequency-pullout torque was evaluated by incorporating it in the motor shown in FIGS. As a reference, as in Experiment 1, a stator yoke in which an outer yoke made of SUY and an inner yoke were combined was incorporated into the motors of FIGS. 2 and 3 and the driving torque was evaluated. The result is shown in FIG. 7 (relative value 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 inner yoke plated with the nickel-iron alloy of Examples 1 to 7 and the outer yoke made of SUY were combined. Examples 1 to 7 showed substantially the same driving torque.

<Experiment 3>
The stator yoke obtained by combining the outer yokes 12 and 13 and the inner yokes 14 and 15 having the nickel-iron alloy plating of Example 3 obtained in Experiment 1 and Experiment 2 was incorporated in the motor shown in FIGS. . Then, the motors of the outer yoke made of SUY, which is a reference product, and the motors of the inner yoke were compared with the driving torque. The result is shown in FIG. The torque was found to be high at all frequencies in the motor of the combination of the outer yoke and the inner yoke made of nickel-iron alloy plating in Examples 1-7. In addition, this combination of electroformed yokes showed the highest torque compared to Experiments 1 and 2.

<Experiment 4>
The effectiveness when the nickel-iron alloy was plated on the output shaft 23 of FIGS. 2 and 3 was examined. The output shaft 23 shown in FIGS. 2 and 3 was made from a SUY rod by cutting. As in Experiment 1, the output shaft 23 was placed in the basket 30 and plated with nickel-iron alloy. It plated on the plating conditions of Examples 1-7. The target plating thickness was 5 μm. It was built in the motor of FIG.2 and FIG.3, and the rotation durability test was done. The test was performed under conditions of 500 PPS and no load. As a reference, the output shaft 23 in FIG. 2 and FIG. 3 was made by cutting from a SUY rod, and then subjected to an electroless nickel plating of 5 μm for a durability test. In addition, a comparative example was also made of a product obtained by cutting the output shaft 23 from a bar made of SUS303.

  As a result of the durability test, the output shaft subjected to nickel-iron alloy plating under the plating conditions of Examples 1 to 7 was not scraped or changed in torque characteristics at 300,000 revolutions, but subjected to electroless nickel plating. The output shaft was 100,000 rotations, and the output shaft of SUS303 material was 150,000 rotations.

(Comparative Examples 1-3)
The outer yokes 12 and 13 and the inner yokes 14 and 15 were plated with a thickness of 20 μm in the same procedure as in Experiment 3 of Examples 1 to 7 under the conditions of Comparative Examples 1 to 3 in FIG. Torque was measured by manufacturing a motor with the outer yokes 12 and 13 and the inner yokes 14 and 15 plated in Comparative Example 1, but the motor torques of the outer yokes 12 and 13 and the inner yokes 14 and 15 manufactured with SUY in Experiment 1 were measured. It was the same torque compared with, and the effect of plating was not seen. When the iron content is about 1%, the characteristics of iron become dominant, and it has been found that there is no effect of nickel-iron alloy plating. In addition, the durability test was performed by plating the output shaft in the same procedure as in Experiment 4. However, as with the electroless nickel plating, scraping occurred at 100,000 revolutions, and the torque was reduced. This seems to be because the hardness decreased and the dynamic friction coefficient increased. In the case of the condition of Comparative Example 2, the plating could not be formed well. Moreover, in the case of the conditions of the comparative example 3, since the crack generate | occur | produced during plating, plating could not be formed.

<Evaluation of magnetic properties>
FIG. 5 shows the mass% of iron, saturation magnetic flux density, and specific resistance of the electroformed nickel-iron alloy. The thickness of the plating is 20 μm. As a result of evaluation by incorporating a yoke made of nickel-iron alloy into a motor, the higher the iron content, the higher the magnetic flux density and the higher the specific resistance. From the results of this example, it was found that the specific resistance is more important than iron than the magnetic flux density. 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 plating with an iron content of 3 to 60% by mass is 400 or more, it is hard to be deformed because the hardness is 5 times or more that of the yoke made of SUY. Further, the dynamic friction coefficient of nickel-iron alloy plating is 0.3 to 0.4, which is smaller than the dynamic friction coefficient 0.6 of electroless nickel plating and the dynamic friction coefficient 0.5 of SUS303, so that the wear resistance is excellent.

  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 regarding the manufacturing method of the electroformed outer 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. It is a disassembled perspective view which shows the structural example of the motor shown by FIG. 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.

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 23 Output shaft 30 ３１ 31 Nickel-iron alloy plating solution 32 Anode 33 Cathode 101 Bobbin 102 Stator yoke 103 Case 105 Stator coil 106 Yoke 106a, 106b Stator tooth 108 Bearing 109 Rotor 110 Output shaft 111 Rotor magnet 115 Flange

Claims (3)

In a motor equipped with a yoke made of iron as a magnetic circuit excited by a coil,
On the surface of the yoke , a plating film made of a nickel-iron alloy containing sulfur and having an iron content of 3 to 60% by mass and a sulfur content of 0.002 to 0.12% by mass is 20 μm or more. A motor characterized by being formed. A rotor magnet fixed to a rotating shaft that is rotatably supported, a yoke made of an iron material having a magnetic pole facing the rotor magnet and facing the gap, and a coil that excites the yoke. In the motor with
On the surface of the yoke , a plating film made of a nickel-iron alloy containing sulfur and having an iron content of 3 to 60% by mass and a sulfur content of 0.002 to 0.12% by mass is 20 μm or more. A motor characterized by being formed. In a motor having a rotor magnet fixed to a rotating shaft that is rotatably supported, a yoke that forms a magnetic circuit having a magnetic pole facing the rotor magnet with a gap therebetween, and a coil that excites the yoke ,
On the surface of the output shaft, 5 μm of a plating film made of a nickel-iron alloy containing sulfur and having an iron content of 3 to 60% by mass and a sulfur content of 0.002 to 0.12% by mass A motor formed as described above .

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