JPS6346669B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a coreless armature in which at least the armature winding portion is integrally made rigid by heating and curing a wet thermosetting resin composition containing microcapsules containing a foaming agent as an essential component. The armature winding is generally made by winding a predetermined number of electric wires and using a binder such as varnish to make the armature winding integrally rigid together with the supporting iron core. However, in the case of an armature winding without a supporting core, such as a coreless armature, the armature winding itself must be made integrally rigid by some method. In particular, in the case of relatively large coreless armatures ranging from several watts to several hundred watts, the properties required for integrally rigid body construction are sophisticated, such as strength at high temperatures, dimensional stability, thermal shock resistance, and electrical insulation. An integrally rigid body is required that can meet the requirements for durability and long-term heat deterioration resistance. Therefore, transfer molding is applied to at least the armature winding portion of the above-mentioned coreless armature using a thermosetting resin containing an inorganic filler of 50% or more, and prepreg hardening is further applied to a part of the surface of the armature winding. Iron-free armatures that utilize the combined effect of providing layers have been put into practical use. The transfer molding used for such iron core armatures is
First, the armature winding is placed in a mold, and a thermosetting resin is injected by applying pressure from outside the mold to form an integral rigid body. However, according to such a transfer molding method, in order to fill every corner of the mold with the thermosetting resin, the injection pressure increases rapidly due to the viscosity of the resin at the end of resin injection. Therefore, there were problems in that the armature winding moved within the mold, causing armature imbalance and deterioration of insulation. In addition, many of the relatively large ironless core armatures mentioned above, ranging from a few watts to several hundred watts, are used as motors to perform incremental operations by taking advantage of their quick response, and are used in fields that cannot be followed by pulse motors, such as They are often used in fields such as magnetic disks, facsimile machines, automatic welding machines, industrial robots, and machine tools, but as these devices become more sophisticated and precise, motors with even higher control responsiveness, In other words, the emergence of a low-inertia iron-core armature was desired. The present invention has been made in view of the above-mentioned demands, and relates to a manufacturing method for the purpose of lowering the inertia of a coreless armature in which at least the armature winding portion is made into an integral rigid body by heating and curing a thermosetting resin. It is. That is, in a method for manufacturing a coreless armature in which at least the armature winding portion is integrally made rigid with a thermosetting resin in a mold, microcapsules containing a polymerization initiator, a filler, and a foaming agent are used. Using a wet thermosetting resin which is an essential component and whose heat curing temperature is higher than the heating expansion temperature of the microcapsules, this thermosetting resin is placed on the commutator side coil terminal of the armature winding, Heating after mold clamping,
The foaming agent contained in the thermosetting resin is expanded, and the expansion pressure causes the thermosetting resin to fill the mold including the end portion of the coil on the side opposite to the commutator. It is characterized by making it a rigid body. The present invention will be explained in more detail below. Wet-type thermosetting resin has as an essential component microcapsules containing a blowing agent placed on the commutator side coil end (rotation center side) of the armature winding.The microcapsules containing the blowing agent expand. The inside of the mold is filled by pressure. At this time, there is a large amount of resin at the end of the coil on the commutator side in the mold, and the pressure of the resin increases between it and the mold, so the expansion of the microcapsules containing the foaming agent is small, but on the side opposite to the commutator. Since there is a large amount of space at the end of the coil (circumferential portion), the thermosetting resin moves toward the side opposite to the commutator, and the microcapsules containing the foaming agent expand significantly. Therefore,
The resin can be spread throughout the mold by the expansion pressure of the microcapsules containing the foaming agent, and in the armature, the expansion of the microcapsules containing the foaming agent is small on the commutator side, and the expansion pressure of the microcapsules containing the foaming agent is small on the armature side. The expansion of the microcapsules containing the blowing agent increases,
The density distribution can be made such that the density decreases from the commutator side of the armature to the counter-commutator side (from the rotation center side to the circumferential side). The iron-core armature targeted by the present invention is used as a motor with power ranging from several watts to several hundred watts, and if it is a wire-wound type iron-core armature, its shape is flat. There is no problem even if the shape is straight or cup-shaped. The thermosetting resin used in the present invention includes a basic resin, a compound capable of curing it, or a polymerization initiator, microcapsules containing a blowing agent, a filler, fibers added as necessary, a mold release agent, It refers to a wet foamable resin composition consisting of a colorant and preferably having a foaming ratio of 1.5 to 2.5 times. The basic resin includes unsaturated polyester, urethane, epoxy, etc., and among them, unsaturated polyester is preferable. The unsaturated polyester used in the present invention refers to α, β unsaturated carboxylic acids or these, saturated dicarboxylic acids, organic acids including saturated and unsaturated monocarboxylic acids, and alcohols, such as glycols and polyhydric alcohols. An unsaturated polyester obtained by an esterification reaction with monovalent alcohols and monohydric alcohols is dissolved in a crosslinking monomer that can be polymerized with the unsaturated polyester, and usually contains a small amount of a polymerization inhibitor, and if desired, a low Shrinking agents include polystyrene, polyethylene, polymethyl methacrylate and copolymers thereof, polyvinyl chloride, and polycaprolactone-saturated polyester. In the case of the above-mentioned unsaturated polyester, the curing agent or polymerization initiator includes organic peroxides such as benzoyl peroxide and methyl ethyl ketone peroxide, and the accelerator includes metal salts such as cobalt naphthenate and cobalt octoate. Amines such as triethanolamine, diethylaniline, etc. are optionally used. The microcapsules containing the blowing agent, which is an essential component of the thermosetting resin according to the present invention, are made of, for example, acrylonitrile-vinylidene chloride copolymer, polystyrene, poly-α-methylstyrene, polyisobutylene, etc. In addition, substances that generate gas when heated include dinitrosopentamethylenetetramine, azodicarbonamide, toluenesulfonylhydrazide, azoisobutylnitrile, propane, pentane, hexane, heptane, petroleum ether, dichloropentane,
It refers to a substance containing aliphatic and cyclic aliphatic hydrocarbons that do not dissolve fine capsule substances such as cyclopentadiene. In addition, fillers such as calcium carbonate, hydrated alumina, and silica, fibers such as glass and vinylon, mold release agents such as zinc stearate and calcium stearate, coloring agents such as titanium oxide, phthalocyan blue, and carbon black, and oxidized A metal crosslinking agent such as magnesium is used as appropriate and necessary. Note that the relationship between the steps and temperature in the present invention will be explained below. The above-mentioned polymerization and curing of the wet thermosetting resin containing microcapsules containing a blowing agent as an essential component is usually accompanied by heat generation. The viscosity increases due to polymerization and oxidation while generating heat, and eventually hardens. Even if the polymerization is carried out at a relatively low temperature at this time, once the polymerization has started, the temperature will normally rise to a fairly high temperature, and at that point the viscosity of the thermosetting resin will also increase significantly. The expansion pressure of the microcapsules encapsulating the foaming agent contained in the plastic resin is insufficient to fill the area opposite to the commutator in detail. Therefore, it is necessary to reach a temperature at which the microcapsules containing the blowing agent expand while the viscosity is still low at the initial stage of polymerization. In addition, the temperature at which the armature winding becomes integrally rigid is below the minimum temperature at which the microcapsules containing the foaming agent expand.
Alternatively, if the temperature is close to that temperature, due to the time delay in heat conduction, the microcapsules containing the blowing agent in the thermosetting resin reach the expansion temperature due to the polymerization heat after polymerization has started, and the viscosity has already increased. This is extremely likely to cause incomplete filling in the mold, making it impossible to obtain the desired iron-free armature. In other words, in order to raise the temperature to the inside of the system above the expansion temperature of the microcapsules enclosing the foaming agent without using polymerization heat, it is necessary to make the armature integral stiffening temperature, that is, the heating hardening temperature, higher than the foaming temperature. be. Furthermore, if the microcapsules enclosing the foaming agent are expanded in the mold before polymerization starts, if left in that state for a long time, the foamed microcapsules may be destroyed again by the molten resin or crosslinked monomer. There is. Therefore, a thermosetting resin is placed on the commutator side coil end of the armature winding in a mold, the mold is clamped, and the expansion pressure of the microcapsules containing the foaming agent contained in the thermosetting resin is applied. Therefore, it is desirable to adjust the temperature so that once the thermosetting resin is filled up to the end of the coil on the side opposite to the commutator of the armature winding, the thermosetting resin quickly polymerizes, increases the viscosity, and hardens. As long as the viscosity increases to a certain extent, even if the microcapsules are destroyed, they will remain as small cells in the void, and the density is higher at the coil end on the commutator side, and lower density closer to the coil end on the anti-commutator side. This results in a low inertia ironless armature. Therefore, the compound or polymerization initiator capable of curing the base resin is preferably an initiator that decomposes at least at a temperature slightly lower than or at the same level as the lowest temperature at which the microcapsules enclosing the blowing agent can expand. Further, as another condition of the present invention, a thermosetting resin is placed on the commutator side coil end portion of the armature winding,
Since the mold is immediately clamped, there is a risk that the armature winding will be crushed by the thermosetting resin, so the thermosetting resin must be a wet type. By immediately clamping the mold using a wet thermosetting resin, the thermosetting resin is heated uniformly from both sides of the mold, and in its low viscosity state before polymerization and hardening, it is blown by the expansion pressure of the foaming agent or the microcapsules surrounding it. This will lead to complete filling. Examples are shown below. [Example] A flat armature winding consisting of a commutator and an armature winding group consisting of 23 single coils made of 50 turns of insulated wire with a self-bonding layer of φ0.25 arranged in a flat shape was prepared. did. Further, a wet thermosetting resin composition containing microcapsules having the following composition was kneaded in a kneader using microcapsules containing isobutane in capsules made of acrylonitrile-vinylidene chloride copolymer. Unsaturated polyester 70 parts by weight Styrene 80 parts by weight Microcapsules 3.5 parts by weight Benzoyl peroxide 1 part by weight Calcium carbonate 200 parts by weight Zinc stearate 2 parts by weight 15 g of the above thermosetting resin was preloaded into the mold into an armature. After placing it on the commutator side coil end of the winding and closing the mold, it was made into an integral rigid body at a heating temperature of 130°C and a mold clamping time of 3 minutes to obtain a flat coreless armature with an outer circumference of φ94. [Comparative Example 1] Epoxy resin molding material containing 75% by weight of silica
Using 50g, create an armature winding with the same configuration as in the example.
A coreless armature made into an integrally rigid body was obtained by transfer molding using the conventional method at 160℃. [Comparative Example 2] Using 25 g of the thermosetting resin used in the example, a coreless armature made into an integrally rigid body was obtained by transfer molding using the same conventional method as in Comparative Example 1. The weights of the coreless armatures obtained in the above Examples and Comparative Examples and the densities of the polymerized and hardened thermosetting resins of the commutator side coil end portions and the non-commutator side coil end portions are shown in the table below.

[Table] The above armature winding weight is 52.9g, and the commutator is
The thermosetting resin used in the examples has an expansion ratio of 1.9 to 2.2 times. As is clear from the above table, the total weight of the embodiment of the present invention is 18% compared to the iron-core armature of Comparative Example 1, which is made of an epoxy resin molding material that has been put into practical use.
Achieved weight reduction of ~20%. In other words, the motor achieves a reduction in inertia of 18 to 20% and operates with extremely excellent control responsiveness. moreover,
Compared to Comparative Example 2, in the present invention, the mechanical strength of the ironless armature is high because the thermosetting resin polymerized and hardened in the central part where mechanical strength is most required when using the ironless armature has a high density. On the other hand, since the thermosetting resin polymerized and hardened at the end of the coil on the side opposite to the commutator, which has a large effect on reducing the inertia of the motor, has a low density.
Compared to Comparative Example 2, the motor control response is further improved by 3~
Improve by 5%. Furthermore, as shown in the above table, the iron-core armature according to the present invention has a particularly lightweight thermosetting resin polymerized and hardened at the end portion of the coil on the side opposite to the commutator, which corresponds to the outer periphery of the armature, so that the amount of armature unbalance is reduced. Moreover, since the expansion of the microcapsules spreads the resin into the mold, it is possible to prevent deformation and misalignment of the armature windings, resulting in a motor with stable quality.

Claims (1)

[Claims] 1. In a method for manufacturing a coreless armature in which at least the armature winding portion is integrally made rigid with a thermosetting resin in a mold, microcapsules containing a polymerization initiator, a filler, and a foaming agent are used. Using a wet thermosetting resin that is an essential ingredient and has a heating curing temperature higher than the heating expansion temperature of the microcapsules,
This thermosetting resin is placed on the commutator-side coil end of the armature winding, and after the mold is clamped, it is heated to expand the foaming agent contained in the thermosetting resin. A method for manufacturing a coreless armature, characterized by filling a mold including a coil end portion on the opposite side of a commutator with a thermosetting resin, and forming an integrally rigid body through polymerization and curing.