JPH0324133B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stepping motor, and more particularly, to a stepping motor that reduces costs and improves motor characteristics by sometimes using new materials for magnetic path components. be.

Conventionally, laminated products and sintered products have been used as rotors and stators that constitute the magnetic path of stepping motors. By the way, the purpose of using the former laminated product is to improve the high frequency characteristics of the motor, and by increasing the specific resistance of the resulting laminated product by providing interlayer insulation through lamination, it is possible to reduce eddy currents in the high frequency range. This is achieved by reducing losses, but a major drawback when using such laminated products is that the manufacturing process includes difficult steps such as laminating thin sheets, and the process is complicated. As a result, there is an inherent problem in causing a significant increase in costs.

On the other hand, when using the latter sintered product as a magnetic path component, the purpose is to simplify the manufacturing process even if it sacrifices the high frequency characteristics of the motor to some extent, and to compare it with the laminated product described above. The goal is to achieve lower production costs. However, the problem with using this sintered product is that, as mentioned above, poor characteristics in the high frequency range are unavoidable, and a high temperature of 1000 to 1200°C is generally used in the sintering process. In addition, it is difficult to say that a sufficient cost reduction has been achieved due to the necessity of adjusting the atmosphere in the furnace for sintering.

The present invention has been made against this background, and its purpose is to simplify the manufacturing process of the rotor and stator, which are the magnetic path constituent members of a stepping motor, and to reduce the cost thereof. While aiming at improving the characteristics of the motor.

Accordingly, the present invention is formed by pressure molding a composite powder that is based on magnetic powder and has a thermosetting resin blended therein as a binder at a ratio of 0.5 to 2.0% by weight. A part or all of the rotor and/or stator of a stepping motor is constructed using a molded product in which the thermosetting resin is cured simultaneously with or after the pressure molding. This is how the object of the present invention can be effectively achieved.

That is, according to the present invention, magnetic path constituent members such as the rotor and stator of a stepping motor are simply formed by adding composite powder of iron powder (magnetic powder) and thermosetting resin, as illustrated in FIG. Since it can be manufactured by pressure molding and curing the resin, compared to the complicated and long manufacturing process of a conventional magnetic path component made of a laminated product as shown in FIG. The process could be significantly shortened and simplified, and the temperature of the thermosetting process was much lower than the manufacturing process of the magnetic path component made of the conventional sintered product shown in Figure 3. The temperature is much lower (approximately 1/6 or less) than the bonding process (approximately 1000 to 1200℃), and the time is shortened to approximately 60 minutes, reducing energy consumption such as electricity during manufacturing. The amount could be significantly reduced.

In addition to this significant reduction in energy consumption, the present invention eliminates the need for vacuum maintenance or atmosphere adjustment using reducing gas, which is required in the conventional sintering process. This resulted in a significant cost reduction of magnetic path components such as the stator and the stator, and in turn, the cost of the stepping motor could be reduced.

In addition, in the conventional sintered product manufacturing process, strict dimensional accuracy is required for the magnetic path components of stepping motors, so a sizing process is inserted after the sintering process, which improves the dimensional accuracy of sintered products. However, since the hardened pressure molded product according to the present invention has extremely excellent dimensional accuracy, there is no need to adopt a sizing process, and the molded product after the hardening operation can be used as a magnetic path component. It has the great feature of being able to be used as a rotor or stator.

Furthermore, the stepping motor according to the present invention comprises:
Compared to conventional stepping motors that use sintered products for the rotor and stator that constitute the magnetic path, the motor characteristics, sometimes pull-in in the high frequency range, are
This resulted in effective improvements in IN) characteristics and pull-out (PULL-OUT) characteristics.

The magnetic powder used in the present invention is generally pure iron powder, particularly electrolytic iron powder, but other magnetic powders may be used. Using such magnetic powder as a base, a predetermined amount of thermosetting resin is blended as a binder to form a composite powder. For example, other additives can be blended together in order to improve lubricity or the performance required of magnetic path components.

By the way, the proportion of magnetic powder constituting such a composite powder will be determined appropriately according to the performance required of the magnetic path component, but it is also related to the amount of thermosetting resin used, and generally It is used at a rate of 96% or more, preferably 98% or more.

In addition, as the thermosetting resin which is another essential component of the composite powder in the present invention, well-known room temperature curing type or heat curing type such as epoxy resin and phenol resin are used. The magnetic powder is uniformly mixed with the magnetic powder. This thermosetting resin contributes to the bonding of magnetic powder, and the greater its content, the greater the strength of the final pressure-molded product (magnetic path component), but it also affects the motor characteristics. In connection with
The blending amount (ratio in the composite powder) will be 0.5 to 2.0% by weight. In particular, when a large amount of thermosetting resin, exceeding 2% by weight, is used, a problem arises in which the resin blows out onto the surface of the molded product, and undesirable deterioration in motor characteristics has also been observed.

Further, the composite powder of magnetic powder and thermosetting resin is supplied to a mold and pressure-molded (press molding or compression molding) in order to form a predetermined magnetic path component. Through this, magnetic path constituent members such as the rotor and stator of a stepping motor or a part thereof are formed, but in the molded product obtained, the thermosetting resin that binds the magnetic powder is preferably heated. By being cured (crosslinked) under conditions,
To provide a molded product with sufficient strength as a magnetic path component. Note that this curing (crosslinking) operation is generally performed on the molded product after pressure molding, but it is also possible to perform an operation such as heating at the same time as the pressure molding to harden the thermosetting resin. It is also possible to do so. In particular, such a curing operation
This is effectively done by heating the resin to a temperature below the decomposition temperature, generally below 300°C, preferably around 120°C to 200°C. There is no need to place the molded product in an atmosphere, and the curing reaction can proceed sufficiently simply by heating in the atmosphere, and the cured molded product with the desired performance, in other words, the magnetic path component or a part thereof can be cured. It can be formed. Furthermore, if necessary, it is also possible to mix a curing catalyst or the like into the composite powder to advance or accelerate the curing reaction.

The dimensional accuracy of the thus obtained cured molded article is significantly improved by the pressure molding operation, and sufficient strength is imparted by the curing reaction. It can be effectively used as it is as a magnetic path forming member such as a rotor or stator, or as a part thereof,
Therefore, the manufacturing process was further simplified and shortened, and the motor characteristics were also improved.

Examples will be shown below to clarify the present invention more specifically, but it goes without saying that the present invention is not limited in any way by the description of these Examples. Note that all parts and percentages in the examples are expressed on a weight basis unless otherwise specified.

Example 1 99 parts of electrolytic iron powder was used as the magnetic powder, and powdered epoxy resin [Sumitomo 3M Co., Ltd.] was used as the thermosetting resin.
Using a composite powder obtained by uniformly mixing one part of Scotch Cast No. 260 (one-component) manufactured by Co., Ltd.,
^Stepping motor stator (inner diameter: 25 mm, outer diameter: 54 mm, thickness: 10 mm) and rotor (outer diameter: 25
mm, thickness: 10 mm), 180℃ x 1
A heating operation was performed for a certain period of time to heat and cure each.

The thus obtained hardened molded stator or hardened molded rotor was set in a known stepping motor, and the motor We investigated the characteristics.

First, FIG. 4 shows measurement results of frequency characteristics of torque with respect to continuous response frequency when various materials are used for the stator of a stepping motor. The rotors of the motors are all made of sintered pure iron, and measurements are taken at a constant voltage of 20V.

As is clear from FIG. 4, the stepping motor equipped with a hardened molded stator according to the present invention is not as good as the motor using a laminated product for the stator in the measurement frequency range, but the difference in characteristics decreases in the high frequency range. It can be said that there is a trend. On the other hand, compared to motors using sintered stators, PULL-IN
There is data that exceeds the high frequency characteristics of 460Hz or higher for the characteristics and 540Hz or higher for the PULL-OUT characteristics.

Next, FIG. 5 shows measurement results of frequency characteristics of torque with respect to self-starting frequency when various materials are used for the rotor of a stepping motor. In addition, the stator of the motor is 0.5
A laminated product using mm-thick electric iron plates is used, and
Measurements are performed at a constant voltage of 20V.

As shown in FIG. 5, the stepping motor equipped with the hardened molded rotor according to the present invention is superior to the motor using a sintered rotor in terms of frequency characteristics above 440 Hz, and is almost superior in the frequency range below that. It is clear that there is no difference.

Therefore, a stepping motor in which a hardened molded product of magnetic powder is used as a magnetic path component such as a stator or a rotor according to the present invention can be used satisfactorily as a motor, and at least the magnetic path component made of a sintered product can be used satisfactorily. It was determined that the stepping motor used in the previous example could be replaced.

Example 2 Composite powders made by using three types of electrolytic iron powders with different particle size distributions as magnetic powders and blending them with epoxy resin in various proportions were molded at a surface pressure of 6 ton/cm ² , and then Example 1 Various powder magnetic cores were obtained by heating and curing under the same conditions as above.

Measured values for each characteristic of the powder magnetic core thus obtained are shown in FIGS. 6 to 8, with the amount of resin contained on the horizontal axis. Note that a in Figures 6 to 8 is for 25 to 30 meshes; 4 parts; 35 to 50 meshes; 7 parts; 50 to 100 meshes; 5 parts and 100 meshes below; 4 parts. This is the result of a powder magnetic core using electrolytic iron powder, and b is 14 ~
20 mesh; 1 part; 35 to 50 mesh; 1 part and 100 mesh below; 1 part; These are the results of a powder magnetic core using electrolytic iron powder consisting of 1 part of 100 mesh and 1 part of 100 mesh.

First, Figure 6 shows the relationship between resin content and magnetic flux density, which is directly related to the motor and its characteristics, but it shows that an increase in resin content causes a decrease in magnetic flux density. In particular, it has been shown that when the amount of resin exceeds 2.0%, the motor characteristics are significantly adversely affected.

Further, FIG. 7 shows the relationship between the resin content and the apparent resistivity, and it is shown that as the resin content increases, the resistivity also increases. Increasing this specific resistance is particularly effective for high frequency characteristics among motor characteristics.
As far as you can see from the graph, the resin amount is 0.5 to 2.0
Within the range of 1.0%, the apparent resistivity is on the order of approximately 10 ^-1 Ω·cm, and even if the amount of resin is 1.0% or less, there is no problem in forming the powder insulating film, and this is sufficient for practical use as a motor.

Furthermore, FIG. 8 shows the relationship between the resin content and the radial crushing strength after thermosetting, and as the resin content increases,
It is clear that the strength increases. However, among the same iron powders, there is only a difference of about 1 Kg/mm ² between 0.5% and 2.0%, and the difference between the types of iron powder is actually larger. Overall, even with a resin content of 1.0% or less, it shows a strength of approximately 10 Kg/mm ² , which is not as high as 20 Kg/mm ² or more for sintered products, but it is suitable for powder magnetic cores used in stepping motors. The strength is a sufficiently practical value.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing the manufacturing process of a magnetic path component according to the present invention, and FIGS. 2 and 3 are manufacturing process diagrams of a conventional magnetic path component made of a laminated product and a sintered product, respectively. 4 and 5 are graphs showing the relationship of torque to continuous response frequency and the relationship of torque to self-starting frequency, respectively, obtained in Example 1, and FIGS. 6, 7, and 8 are graphs, respectively. 3 is a graph showing the relationship between resin content, magnetic flux density, apparent resistivity, and radial crushing strength after thermosetting determined in Example 2.

Claims (1)

[Claims] 1. It is formed by pressure molding a composite powder that is based on magnetic powder and has a thermosetting resin blended therein as a binder at a ratio of 0.5 to 2.0% by weight, and 1. A stepping motor characterized in that a part or all of a rotor and/or a stator is formed of a molded product obtained by curing the thermosetting resin at the same time as molding or after the pressure molding.