JPH1089298A - Manufacture of impeller for blower - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ideal impeller for a blower freed from a shrinkage and a warp during molding even when a vane has a thick wall by a method wherein microcapsules having a thermal expansion property are mixed in a thermoplastic resin material to effect injection molding. SOLUTION: A manufacturing method for an impeller for a blower is such that microcapsules having a thermal expansion property are worked in a pellet- form manner once and a plurality of blade parts 2 and a hub part 3, of which an impeller 1 for a blower consists are injection-molded by using a material prepared by mixing the pellets in thermoplastic resin. In the injection molding thereof, a part of the microcapsules having the thermal expansion property are expanded into fine hollow spherical bodies at the mixing process of an injection molding machine. Thereafter, a material is injected in a cavity in a state that a 10-30% space part remains. By a molten resin after injection and the surplus heat of the microcapsules, the non-expansion parts of the microcapsules are expanded in a manner that the cavity is fully filled therewith and the fine hollow spherical bodies are uniformly dispersed in a molded product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of processing a heat-expandable microcapsule into pellets, mixing the pellets with an olefin-based thermoplastic resin material, etc. The present invention relates to a method for manufacturing an impeller for a blower having a hollow hollow sphere. The objective is to improve the efficiency (noise and total pressure efficiency of the blower, the static pressure efficiency), to reduce the weight of the molded product and to shorten the molding time, and to improve the productivity.

[0002]

2. Description of the Related Art Heretofore, blowers of this type have often been used by metal press working, but in recent years, blowers by resin molding have come to be used frequently. In this type of blower, in order to improve the performance, the impeller blade section shape is changed to NACA series or Gotting.
It is recommended that the shape be based on the wing theory such as en cascade. In this case, the blade sectional area is set to a blade shape based on a so-called streamline. For example, an impeller used for an outdoor unit of a home air conditioner has a diameter of about φ300 mm, so that the maximum thickness of the blade is theoretically about 15 mm.

[0003] By injection molding of this thickness, irregularities occur on the surface of the blade due to sink and warpage due to thermal shrinkage of the resin, and a laminar flow along the surface of the blade separates to generate turbulent flow. Generated noise increases.
In order to prevent the above-mentioned sink marks and warpage, the cooling time is lengthened and the cooling is gradually performed. However, this results in an increase in the molding cycle time and a reduction in productivity. Conventionally, therefore, mainly due to manufacturing restrictions, in the case of resin molding, the blade portion shape (for example, 2 mm) having a uniform thickness conforming to the intermediate cross-sectional shape of the theoretical shape or the shape on the pressure surface side.
４4 mm).

In recent years, a method such as a hollow molding method or a two-time molding method has been adopted as a means for realizing a thick-walled wing according to the wing theory by resin molding. In the former hollow molding method, after injecting the thermoplastic molten resin into the mold cavity,
An impeller molding method for press-fitting an inert gas such as compressed nitrogen into the cavity to form a hollow portion inside a plurality of blades. Further, in the latter twice molding method, the thick part is divided into two parts, and the thick part is first molded into a half thick part, and then the remaining part is molded again. .

In addition, in the conventional injection molding method, a large amount of talc or layered mica is finely pulverized and mixed with mica as a dimensional stabilizer in order to prevent deformation after being removed from a mold. The reason is that the blade portion of the impeller 1 for the blower becomes cantilevered from the hub portion and is taken out of the mold after molding, and is easily deformed downward by its own weight. This is because it is necessary to take it out at a stage where it has been cooled to some extent from the viewpoint of productivity.

On the other hand, various products using glass hollow beads have been proposed in order to reduce the weight of the products. For example, Japanese Utility Model Application Laid-open No. Sho 59-182463, Japanese Utility Model Application Laid-open No. Sho 59-1824.
The lightweight handle shown in No. 64.
No. 411.

[0007]

However, in the above-mentioned hollow molding method, it is not possible to control the thickness of the resin uniformly by injection gas filling as well as injection molding. This can be achieved by making the viscosity, temperature, injection pressure, and injection amount of the resin flowing into all blade portions exactly the same, but it is impossible to realize this by actual injection molding. The hollow part of this was a matter of course.

Further, since the impeller for the blower is a rotating body, it is naturally necessary to balance the weight.
As specified in JISB0905 "Good balance of rotating equipment", it is necessary to correct the weight imbalance depending on the purpose of use in order to suppress the vibration and noise of the rotating body.

However, as described above, if the hollow portion is left as it is, the weight balance is also left as it is.
When a large weight imbalance occurs, it cannot be completely corrected even if the balance is corrected in a subsequent process. Therefore, the above-described molding method is performed twice, but the cycle time is greatly increased, and it cannot be said that the molding method is efficient.

[0010] In the twice molding method, the weight becomes very large because the thick portion, which is about 15 mm, becomes solid.
Since the starting torque of the motor is required, the capacity of the motor is increased, and the efficiency cannot be improved.

Although talc and mica are effective as dimensional stabilizers, they have disadvantages of heavy weight, and have limited effects as sink and deformation preventing materials. The reason is that mica is a scale-like inorganic substance and is effective for improving dimensional stability in the length direction, but is not effective for dimensional stability such as prevention of shrinkage in the thickness direction.

That is, talc, which is a conventional dimensional stabilizer,
As described above, mica is subdivided into irregular surface textures.
When the resin flows into the cavity and solidifies because of the scale-like thin flakes, the degree of hardening differs depending on the surface condition of the additive, and the part where pressure is not applied and the part that is densely filled A sparsely filled portion was formed, resulting in residual stress, and this difference led to deformation after being removed from the mold.

[0013] Further, in various resin products using conventional glass hollow beads, a hollow nozzle supply nozzle is required in addition to the resin injection molding nozzle so that the hollow beads are arranged as a core material of the product. Injection molding was quite complicated.

[0014]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to injection molding of a plurality of blades 2 and a hub 3 constituting an impeller 1 for a blower. Into the material, a mixture of the thermally expandable microcapsules once processed into a pellet form is mixed, and the mixture is injected while leaving a space in the cavity. The microcapsules that are not yet expanded are expanded into fine hollow spheres so that the space inside is completely filled, so even if the cross-sectional wall thickness of the blade is thicker than the conventional method, it can be molded Provided is an impeller for a blower that can be formed into an ideal blade shape that does not cause aerodynamic flow separation due to no distortion due to thermal shrinkage at the time and that can achieve significant weight reduction. It is an object of the present invention.

That is, according to the present invention, a plurality of blade portions 2 constituting the impeller 1 for the blower are made of a material obtained by processing the thermally expandable microcapsules into pellets and mixing the pellets with a thermoplastic resin. In injection molding of the hub 3, a part of the heat-expandable microcapsules is expanded into fine hollow spheres in a mixing step of an injection molding machine, and then a space of 10 to 30% is left in the cavity. The material is injected, and the unexpanded portion of the microcapsule is expanded by the residual heat of the liquid molten resin and the heat-expandable microcapsule after the injection so that the inside of the cavity is completely filled, so that a fine hollow sphere is uniformly formed in the molded product. A method for manufacturing an impeller for a blower, characterized by being dispersed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
Description will be given based on FIG. FIG. 1 is an external perspective view of an impeller for a blower according to the present invention. In the impeller for a blower, a boss 4 for coupling with a motor shaft is formed at the center of a central hub 3, and a plurality of blades 2 are provided around the hub 3. As shown in FIG. 3, the blade portion 2 has the thickest portion attached to the hub portion 3 and becomes gradually thinner toward the outer periphery. Further, the cross-sectional shape of the impeller 2 is an airfoil shape as shown in FIG. 2 and gradually changes from thin to thick to thin. In addition, 5
Is a metal washer that is insert-molded to more securely fit the motor shaft.

Next, the resin material used in the present invention will be described. The impeller of the present invention is formed by injection molding a material obtained by processing thermally expandable microcapsules into pellets and mixing the pellets with a thermoplastic resin. The thermoplastic resin serving as a base material is, for example, an olefin-based resin material such as polypropylene or polyethylene, and the thermoplastic resin has a melting temperature equal to or lower than a temperature at which a heat-expandable microcapsule described later starts to expand by heat. There is no particular restriction as long as it has.

As the pellets to be mixed with the thermoplastic resin, those obtained by processing the heat-expandable microcapsules once into pellets as described above are used. It is formed by pelletizing heat-expandable microcapsules containing a hydrocarbon such as isobutane or isopentane which is gasified by heat inside using a softening thermoplastic resin material as an outer shell resin.
As a specific example of the heat-expandable microcapsules, a hydrocarbon such as isobutane and isopentane is wrapped with a thermoplastic resin having a large gas barrier effect such as a vinylidene chloride / acrylonitrile copolymer. EXPANCEL, Inc.).

Next, how the thermally expandable microcapsules expand during injection molding and are uniformly dispersed as fine hollow spheres (hereinafter, referred to as microballoons) in a molded product will be described. The pellets expand due to heating in the mixing step of the injection molding machine and increase in bulk. This material is injected such that a space portion remains in the cavity by 10 to 30%, and the microcapsules expand until the inside of the cavity is completely filled by the residual heat of the injected molten resin and the thermally expandable microcapsules. I have. In order to efficiently disperse the heat-expandable microcapsules uniformly in the molded product, the heat-expandable microcapsules are not destroyed in the mixing step of injection molding, and are also efficiently dissipated in the cavity of the mold as a product. The point is to expand well.

That is, the above-mentioned expanded microcapsules, that is, microballoons, are just like a vinyl balloon because the outer shell is only about 0.1 μm thick. Therefore, if the molding conditions are not properly selected, the microballoon will be broken in the molding process.

The inventor studied various molding conditions and manufactured the impeller 1 for a blower of the present invention under the following molding conditions. As the compounding ratio of the materials, 90 parts by weight of polypropylene,
10 parts by weight of pellets containing 3 parts by weight of thermally expandable microcapsules were added and mixed. Also, for injection molding, 10 cavities are formed in the cavity of the shape of the impeller 1 for the blower.
Injecting leaving 30% of space part, expand the unexpanded microcapsule by the molten resin after injection and the residual heat of the thermally expandable microcapsule so that the cavity is completely filled, and form a fine hollow sphere It was made to be able to be evenly dispersed in the product. At this time, the temperature of the mixing section of the injection molding machine is 170 ° C. to 180 ° C., the plasticization time is about 50 sec, the injection time is about 3 sec, the cooling time is 60 to 100 sec, and the mold temperature is about 50 ° C.

An impeller 1 for a blower molded under the above molding conditions.
Can reduce the weight by about 40% as compared with the case where no heat-expandable microcapsules are contained. It is possible to obtain an ideal wing shape in which there is no sink mark, warpage or the like in appearance and the weight distribution of each blade is uniform. Since the inside of the microballoon (fine hollow sphere) is hollow, the inside space has a soundproofing effect and noise can be reduced. Since the dispersed heat-expandable microcapsules are instantaneously expanded individually, molding can be performed with almost the same molding cycle time as a normal injection-molded product despite thick molding.

[0023]

As understood from the above description, in the present invention, the blade part 2 and the hub part 3 constituting the impeller 1 for the blower are made of a thermoplastic resin material containing organic microballoons (fine hollow spheres). Since it is formed, the thickness of the blade portion can be formed to an ideal thickness, the weight can be reduced and the productivity can be improved, and its practical effect is extremely large.

[Brief description of the drawings]

FIG. 1 is an external perspective view of an impeller for a blower according to the present invention.

FIG. 2 is a sectional view taken along line AA of a blade portion of the impeller.

FIG. 3 is a longitudinal sectional view showing a state where the impeller is attached to a motor shaft.

[Explanation of symbols]

1. 1. Impeller for blower Blade part 3. Hub part
4. Boss part 5. Washer 6. Motor 7. Motor shaft 8. nut.

Claims (1)

[Claims] 1. A plurality of blade portions 2 and a hub portion 3 constituting an impeller 1 for a blower made of a material obtained by processing a thermally expandable microcapsule into a pellet shape and mixing the pellet with a thermoplastic resin. In injection molding, a part of the heat-expandable microcapsules is expanded into fine hollow spheres in a mixing step of an injection molding machine, and then 10 μm is introduced into the cavity.
This material is injected leaving a space portion of about 30%, and the unexpanded portion of the microcapsule is expanded by the residual heat of the liquid molten resin after injection and the heat-expandable microcapsule so as to completely fill the cavity, and molded. A method for manufacturing an impeller for a blower, characterized in that fine hollow spheres are uniformly dispersed in a product.