JPS6346670B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a coreless armature, in which at least the armature winding portion is made into an integrally rigid body by heating and curing a thermosetting resin. The armature winding is generally manufactured by winding a predetermined number of electric wires and making them integrally rigid together with the supporting core using an adhesive such as varnish. However, even in the case of an armature winding without a supporting core, such as a coreless armature, it is necessary to make it an integral rigid body 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 making them into integral rigid bodies are sophisticated, such as strength at high temperatures, dimensional stability, thermal shock resistance, and electrical insulation. An integrated rigid body is required that can meet the requirements for heat deterioration resistance and long-term heat deterioration resistance. Therefore, transfer molding is applied to at least the armature winding portion of the coreless armature using a sealing resin made of a thermosetting resin containing an inorganic filler of 50% or more, and furthermore, part of the armature winding is One that utilizes the combined effect of providing a hardened prepreg layer on the surface of the part has been put into practical use. Generally, flat motors with a flat shape have a problem in that insulation tends to deteriorate when the diameter of the windings is 0.3 mm or less. This is because when the coil is fixed by injecting the sealing resin into the mold using transfer molding, etc., the injection pressure increases rapidly at the end of the injection, causing the coil to move within the mold. be. Furthermore, relatively large coreless armatures ranging in power from a few watts to several hundred watts are often used as motors in fields where pulse motors cannot follow, and they take advantage of their fast response to perform incremental motion. This is because it is convenient for doing so. In other words, it is widely used in fields such as magnetic disks, facsimiles, automatic welding machines, and machine tools. Therefore, in view of the increasing performance and precision of these devices, there has been a desire for a low-inertia iron-core armature with stable product quality and further improved control responsiveness. The present invention has been made in response to the above requirements, and by heat curing a sealing resin made of a thermosetting resin, at least the armature winding portion is made into an integral rigid body, achieving stable quality and low inertia. The purpose of the present invention is to provide a method for manufacturing a iron-free armature that can be manufactured using the following methods. In order to achieve such an object, the present invention provides a method for manufacturing a coreless armature in which at least the armature winding portion is made into an integral rigid body by heating and curing the thermosetting resin. Microcapsules encapsulating an aliphatic or cycloaliphatic hydrocarbon are mixed into a copolymer of acrylonitrile and vinylidene chloride having a vinylidene chloride content of % or more, and the heating curing temperature of the thermosetting resin is adjusted to the temperature at which the microcapsules expand. The feature is that the temperature is higher than the temperature. The ironless armature to which the present invention is directed is used in motors ranging from a few watts to several hundreds of watts, but a wire-wound type ironless armature can be used even if its shape is flat. There is no problem even if the condition is the same. The thermosetting resin used as the sealing resin used in the present invention includes a basic resin, a compound that can be polymerized and cured with the basic resin, a polymerization initiator, a filler, fibers used as appropriate, a mold release agent, and a coloring agent. It is constructed as an agent. The basic resin includes unsaturated polyester, diallyl phthalate, urethane, epoxy, etc., and among these, unsaturated polyester and diallyl phthalate are preferred. The unsaturated polyester here refers to organic acids including α, β unsaturated carboxylic acids, rarely these, saturated dicarboxylic acids, saturated and unsaturated monocarboxylic acids, glycols,
An unsaturated polyester obtained by an esterification reaction with alcohols such as polyhydric alcohols and monohydric alcohols is dissolved in a crosslinking monomer that can be polymerized with the unsaturated polyester, and there is usually a small amount of polymerization inhibition. If desired, polystyrene, polyethylene, polymethyl methacrylate and copolymers thereof, polyvinyl chloride, and polycaprolactone-saturated polyesters are included as low-shrinkage agents. Furthermore, diallyl phthalate includes prepolymers such as diallyl orthophthalate and tetrachlorodiallyl phthalate, and copolymers thereof, and crosslinking monomers that can be polymerized with these, and if desired, further include rubbers such as butadiene, urethane, etc. Refers to materials containing thermoplastic resins such as polystyrene and polyethylene. The polymerization initiator for the basic resin is an organic peroxide such as benzoyl peroxide, methyl ethyl ketone peroxide, etc., and the polymerization accelerator is a metal salt such as cobalt naphthenate, cobalt octoate, triethanolamine, diethylanili, etc. Amines are optionally used. Calcium carbonate, hydrated alumina, as filler
Silica, etc., fibers such as glass, vinylon, etc.
Calcium stearate is used as a mold release agent, and titanium oxide, phthalocyan blue, carbon black, etc. are used as coloring agents. Vinylidene chloride in microcapsules mixed into thermosetting resin composed of each of the above components.
The acrylonitrile copolymer contains 50% or more of vinylidene chloride, and the aliphatic or cycloaliphatic hydrocarbons included in this copolymer include propane, pentane, hexane, butane, pebtan, petroleum ether, Vinylidene chloride such as dichloropentane and cyclopentadiene
A material that does not dissolve the acrylonitrile copolymer is used. Microcapsules are made by forming a polymer film made of vinylidene chloride-acrylonitrile copolymer around a core material made of aliphatic or cycloaliphatic hydrocarbon, and the core material has the role of vaporizing and expanding in volume when heated. However, the polymer membrane, which has begun to soften, is expanded by the vapor pressure of the core material, expanding the capsule. At this time, a portion of the core substance passes through the membrane and diffuses to the outside of the microcapsule. Therefore, the microcapsules expand by themselves in the warm mold, and the thermosetting resin serving as the sealing resin fills the mold and hardens. Since the manufacturing method using microcapsules is of a self-filling type, the problem of injection pressure can naturally be solved. Polymerization and curing of the thermosetting resin mixed with the above-mentioned microcapsules usually involves a process in which the viscosity increases while generating heat, and finally hardening occurs. During this polymerization and curing, the microcapsules expand inside the thermosetting resin, and as the thermosetting resin progresses, the microcapsules are cured while being expanded. Therefore, the apparent density of the thermosetting resin can be lowered, and the weight of the ironless armature can be reduced. Even if polymerization is carried out at a relatively low temperature, once the polymerization starts, the temperature usually rises to a fairly high temperature, and at that point the viscosity increases significantly, causing the microcapsules contained in the thermosetting resin to Since the microcapsules cannot expand, it is necessary to reach the temperature at which the microcapsules expand while the viscosity at the initial stage of polymerization is still low. On the other hand, if the integral rigidity temperature of the armature winding is below or close to the minimum temperature at which the microcapsules expand, the temperature at which the microcapsules in the thermosetting resin expands due to the time delay in heat conduction. This is due to the heat of polymerization, and at that point the viscosity of the thermosetting resin has already increased significantly and the microcapsules cannot expand. Therefore, in order to raise the temperature of the thermosetting resin and the microcapsules contained therein to a temperature higher than the expansion temperature of the microcapsules without using polymerization heat, it is necessary to increase the temperature at which the armature winding becomes integrally rigid. The temperature needs to be higher than the expansion temperature of the microcapsules. Further, when the microcapsules are expanded in the mold before the start of polymerization, if the microcapsules are left in that state for a long time, the expanded microcapsules may be destroyed again by the molten resin, crosslinked monomer, etc.
Therefore, it is desirable that once the microcapsules expand, they quickly polymerize, increase their viscosity, and harden. This is because, as long as the viscosity increases to a certain extent, even if the microcapsules are destroyed, the voids remain as small cells. Therefore, it is preferable that the polymerization initiator for the basic resin is decomposed at a temperature that is at least slightly lower than or about the same temperature as the temperature at which the microcapsules can expand. As mentioned above, since the mold is filled while expanding the microcapsules, the expansion rate of the capsule is large in the part where the microcapsule has flowed far, and when the sealing resin hardens, the density in that part becomes small. Therefore, it is possible to easily create a distribution in which the density is low at the periphery and increases as the density approaches the center.
In particular, it is possible to naturally achieve weight reduction in thick parts, which has been difficult in the past, and it is possible to significantly reduce the specific gravity. Experimental examples of the present invention will be explained below. [Experimental example] 23 single coils each made of 50 turns of insulated wire having a self-bonding layer of 0.25φ were arranged in a flat shape, and the winding group was connected to a commutator to obtain an armature winding. Further, microcapsules encapsulating isobutane were included in microcapsules of vinylidene chloride-acrylonitrile copolymer having the compositions shown in Table 1 to obtain thermosetting resins having the following compositions. For these microcapsules A to D, the microcapsules were placed in holes with a diameter of 5.6 mm and a depth of 0.3 mm, and were heated at 5°C/min while applying pressure (4.06 mgf/mm ² ) inward from the opening of the hole. The expansion ratio ΔL/L ₀ (ΔL is the expanded length of the microcapsule, L ₀ is the length before expansion) when heated at a rate of is shown in FIG. Furthermore, the relationship between the vinylidene chloride content of the microcapsules and the expansion ratio ΔL/L ₀ (other test conditions are the same as above) is shown in FIG. As shown in the figure, when the vinylidene chloride content is less than 50wt%, the expansion ratio changes rapidly due to a large amount of isobutane permeating through the capsule. With this method, it is possible to obtain stable microcapsules with a stable expansion ratio.

[Table] Thermosetting resin composition Unsaturated polyester 70 parts by weight Styrene 80 parts by weight t-butyl perbenzoate 1 part by weight Calcium carbonate 200 parts by weight Zinc stearate 2 parts by weight Microcapsules 3 parts by weight Contains each of microcapsules A to D A flat coreless armature was produced by placing 15 to 30 g of the thermosetting resin together with the armature winding in a mold preheated to 150° C. and clamping the mold for 5 minutes. The results are shown in Table 2.

[Table] × indicates insufficient filling.
The weight of the armature winding used to manufacture the above iron core armature was 52.9 g, and the weight of the commutator was 24.5 g. As a comparative example, a general epoxy resin molding material was selected and a coreless armature was obtained using armature windings and commutators of the same weight, and the armature weight was 108 g. That is, the weight of the thermosetting resin in such a conventional ironless armature is 30.6 g. On the other hand, when the above microcapsules A or B are used, as is clear from Table 2, the reduction is approximately 50%.
It only weighs 15g, which reduces the weight of the armature as a whole by about 15%. Therefore, it is clear that the inertia of the motor can be reduced. As is clear from the above description, according to the present invention, there is no problem such as deterioration of insulation caused by the movement of the coil within the mold, unlike in the past, and since the specific gravity can be lowered, A lightweight ironless armature can be obtained, and a motor with low inertia can be obtained. Therefore, it is possible to provide a low-inertia iron-core armature with much better control responsiveness than conventional ones.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the relationship between the expansion ratio of microcapsules and temperature in one embodiment of the present invention, and Figure 2 is a characteristic diagram showing the relationship between the content of vinylidene chloride in microcapsules and the expansion ratio of microcapsules. be.

Claims (1)

[Claims] 1. In a method for producing 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 placed in a mold, a thermosetting resin containing a polymerization initiator and a filler is added. , microcapsules containing an aliphatic or cycloaliphatic hydrocarbon as a core material are mixed into capsules made of a copolymer of acrylonitrile and vinylidene chloride containing 50% or more vinylidene chloride, and the thermosetting resin is heated. A method for manufacturing a iron-free armature, characterized in that the curing temperature is higher than the expansion temperature of the microcapsules.