JP2003080548A - Method for manufacturing resin molded products - Google Patents

Abstract

(57) [Problem] To provide a method for manufacturing a resin molded product capable of suppressing residual stress during injection molding as much as possible. SOLUTION: A fluidity promoting material for promoting fluidity is added to a molten resin material 17, and this is injected into a cavity 11 of a mold 10 to produce resin molded products 2 and 3, whereby the molten resin material 17 is produced. Is sufficiently filled into the corners of the cavity 11 with a relatively low injection pressure due to its high fluidity, so that the resin molded products 2 and 3 having high dimensional accuracy can be obtained. The residual stress inside 3 is small and annealing treatment as post-processing is not required or the processing time is shortened. As a result, resin molded products 2 and 3 having good molding accuracy can be obtained at lower cost. it can.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin molded product by injection molding.

[0002]

2. Description of the Related Art Conventionally, a multiblade impeller used for a multiblade fan is generally manufactured by injection molding a resin material.

That is, a multiblade impeller used in a multiblade blower has a rotor-like appearance with a long axial length as shown in FIG. I am supposed to do it. As shown in FIG. 3, this multi-blade impeller 1 normally has a large number of blades 5, 5, ... Standing parallel to a disk-shaped end plate 6 having a support shaft at predetermined intervals in the circumferential direction. The first multi-blade impeller assembly 2 having the installed form, and a large number of blades 5, 5, on the annular end face plate 7 at predetermined intervals in the circumferential direction.
.. A plurality of second multi-blade impeller constituents 3, 3, ... having a configuration in which they are erected in parallel and an end member 4 made of a disk body having a support shaft are individually manufactured. Then, they are obtained by sequentially arranging them in the axial direction and joining and fixing them to each other to integrate them.

By the way, each of the above multiblade impeller constituents 2, 3
And when the end member 4 is manufactured by injection molding,
As shown in FIG. 5, using the injection molding machine 12, the material resin 16 supplied to the hopper 15 is heated and melted in the melt extrusion section 13, and the molten resin material 17 is injected from the injection nozzle 14 into the cavity of the mold 10. It is customary to employ the work procedure of injecting into the cavity 11 and solidifying it within the cavity 11.

In this case, in particular, in each of the multiblade impeller constituents 2 and 3, the blades 5, 5, ... Provided therein have a thin strip shape as shown in FIG. From that,
A portion of the cavity 11 of the mold 10 corresponding to the blade 5 has a thin space and a long depth.
Moreover, in order to reduce the flow resistance of the molten resin material 17 in a state corresponding to the blades 5, 5, ... 5, ... Is ejected from one end side in the length direction, specifically, the side corresponding to the end face plates 6 and 7, and this is injected into each of the blades 5.
In 5, ..., It is customary to flow from one end side to the other end side.

Therefore, each of these multiblade impeller constituents 2, 3
To ensure the dimensional accuracy of the
It is necessary for the molten resin material 17 to be sufficiently spread to every corner of the space where the cavity 11 has a small thickness and a long depth and to be solidified in that state.

From this point of view, in the injection molding of the multiblade impeller constituents 2 and 3, the high pressure injection molding method, that is,
It is customary to employ a method of injecting the molten resin material 17 at a high pressure and sufficiently pushing the molten resin material 17 into every corner of the cavity 11. In this case, in order to prevent shrinkage and shrinkage of the molten resin material 17 injected into the cavity 11 and to maintain the shape, it is necessary to maintain the pressure until the molten resin material 17 is solidified to a predetermined degree. The mold clamping pressure of the mold 10 is also required to be large.

By the way, when the above-mentioned multiblade impeller constituents 2 and 3 are molded by the high-pressure injection molding method, the molded multiblade impeller constituents 2 and 3 are solidified under high pressure. Due to the distortion between the resin molecules caused by, a large residual stress is generated inside. Therefore, when the multi-blade impeller 1 is formed by using the multi-blade impeller constituents 2 and 3 while retaining the residual stress therein, and when the multi-blade impeller 1 is used as a product as it is, the multi-blade impeller is used as a product. The blade impeller constituents 2 and 3 are gradually deformed with the lapse of time, and the accuracy in terms of shape and dimensions of the multi-blade impeller 1 as a product cannot be maintained, which causes vibration or noise during its rotation.

Incidentally, each of the multiblade impeller constituents 2 and 3 as described above.
The residual stress of occurs not only in the injection molding but also in the process of joining the multiblade impeller constituents 2 and 3 to each other.
The residual stress generated here is much lower in level than the residual stress generated during injection molding. Therefore, most of the residual stress in the multiblade impeller constituents 2 and 3 occurs during injection molding. Can be thought of as something.

By removing the residual stress of each of the multiblade impeller constituents 2 and 3 as described above, the accuracy of the shape and dimension of each of the multiblade impeller constituents 2 and 3 as a product and the vibration and noise during rotation. In order to suppress the above, an annealing treatment has been conventionally used. This annealing treatment is a treatment for removing the residual stress in each of the multiblade impeller constituents 2 and 3 by holding the multiblade impeller 1 at a predetermined temperature for a predetermined time after the completion of the molding.

Here, the outline of the manufacturing process of the conventional multi-blade impeller 1 by injection molding will be described with reference to FIG.

This manufacturing process is roughly divided into four steps of an injection molding step 31, a joining step 32, an annealing step 33 and a balancing step 34. The injection molding process 31 includes a mold 10 and an injection molding machine 12 (see FIG. 5).
Is a step of injection-molding each of the multi-blade impeller constituents 2 and 3 described above.

In the next joining step 32, the multi-blade impeller constituents 2 and 3 and the end member 4 produced in the injection molding step 31 are sequentially joined by the ultrasonic joining machine 21, and these are integrated into one body. Obtain the wing impeller 1.

Next, in the annealing step 33, the multiblade impeller 1 is annealed. That is, for example, a large number of the multiblade impellers 1 are arranged in an axial direction in a warm air circulation type annealing furnace 22, and the multiblade impellers 1, 1 ,. Hold for a predetermined time. By this heating and holding, in each of the multiblade impeller constituents 2 and 3, the molecular bond is loosened to facilitate the movement of the molecules, and the strain between the molecules is gradually removed and the residual stress is removed.

Finally, in balancing step 34,
The rotation balance is adjusted by actually rotating the multiblade impeller 1.

[0016]

However, by subjecting the multiblade impeller 1 thus formed to the annealing treatment, the residual stress of the multiblade impeller 1 is removed, and the multiblade impeller 1 is removed.
However, since the annealing furnace 22 is required, the equipment is large in size and the equipment cost is high, and the equipment is large in size. The impeller 1 is likely to have temperature unevenness, so if it is attempted to heat it uniformly, it must be heated and held for a long time (usually 8 to 20 hours), which leads to an increase in operating costs and the manufacture of the multiblade impeller 1. There is a problem in that the work efficiency of the entire process is lowered, and as a result, the product cost of the multiblade impeller 1 becomes high.

Therefore, in the present invention, when a resin molded article is manufactured by injection molding, the occurrence of residual stress at the time of injection molding is suppressed as much as possible, thereby eliminating the need for an annealing treatment as a post-treatment or a processing time thereof. The present invention has been made for the purpose of proposing a method for manufacturing a resin molded product that can shorten

[0018]

In the present invention, the following constitution is adopted as a concrete means for solving such a problem.

In the method for producing a resin molded product according to the first invention of the present application, a fluidity promoting material for promoting fluidity of the molten resin material 17 is added to the molten resin material 17, and this is added to the cavity 11 of the mold 10. It is characterized in that it is injected into the inside to manufacture resin molded products 2 and 3.

In a second invention of the present application, in the method for producing a resin molded product according to the first invention, a gas generating agent that chemically decomposes by heating to generate a gas is used as the fluidity promoting material. It has a feature.

In the third invention of the present application, the above-mentioned first or second
In the method for producing a resin molded product according to the invention, the resin molded products 2 and 3 are multi-blade impellers in which thin plate-shaped blades 5, 5, ... Are concentrically arranged in parallel at predetermined intervals. It is characterized by that.

According to a fourth invention of the present application, in the method for manufacturing a resin molded product according to the third invention, the molten resin material 17 in the portion of the cavity 11 corresponding to the blades 5, 5, ... It is characterized in that the flow direction is set in the longitudinal direction of the blades 5, 5 ,.

[0023]

According to the present invention, the following effects can be obtained by adopting such a configuration.

In the method for manufacturing a resin molded product according to the first invention of the present application, a fluidity accelerating material for accelerating the fluidity of the molten resin material 17 is added to the molten resin material 17, and the mold 10 is used.
The resin molded products 2 and 3 are manufactured by injecting into the cavity 11.

Therefore, according to the method for producing a resin molded product of the present invention, since the fluidity promoting material is added to the molten resin material 17, the molten resin material 17 is injected into the cavity 11 of the mold 10. In this case, since the molten resin material 17 retains its high fluidity, the molten resin material 17 is sufficiently filled in every corner of the cavity 11 even if the injection pressure is set to be relatively low. , A resin molded product 2 having a high shape and dimension accuracy that matches the inner surface shape of the cavity 11.
3 is obtained.

Since the injection molding of the molten resin material 17 can be performed at a low injection pressure as described above, the residual stress inside the resin molded products 2 and 3 is small due to the low injection pressure. Annealing as a treatment is not necessary, or even if annealing is performed, the treatment time can be shortened as much as possible, and the resin moldings 2, 3 can be provided at a lower cost by omitting or simplifying the manufacturing process. You can do it.

Further, since the molten resin material 17 has a high fluidity, the resin molded products 2 and 3 are thin-walled products or thin-walled long products, and the cavity 11 is thin and has a large depth and a small space. However, the molten resin material 17 can be sufficiently filled in every corner of the cavity 11, and the production of a thin resin molded product or a thin long resin molded product becomes easy.

Further, since the injection pressure of the molten resin material 17 at the time of injection molding can be set to be low, the injection molding machine can be downsized or the die 10 can be downsized by lowering the clamping pressure.
That would contribute to the reduction of manufacturing equipment costs.

In the method for producing a resin molded product according to the second invention of the present application, since the gas generating agent that chemically decomposes by heating to generate gas is used as the fluidity promoting agent, The molten resin material 17 is the mold 10
When the gas generating agent is injected into the cavity 11, the gas generating agent is chemically decomposed by the heat of the molten resin material 17 to generate a gas, and the gas molecules intervene between the resin molecules by the molecular motion to separate them. The intermolecular bond is alleviated, and the frictional resistance between the resin molecules accompanied by the flow of the resin molecules is reduced to promote the flow, and the synergistic effect of these reduces the molten resin material 17 injected into the cavity 11. A high fluidity is maintained, and as a result, the same effect as described above is obtained.

Further, in the present invention, since the gas generating agent is used as the fluidity promoting material, the molten resin material 17 injected and filled in the cavity 11 by the expansion force of the gas generated from the gas generating agent is used. It is pressed against the inner surface of the cavity from the inside. Therefore, even if the holding pressure for the molten resin material 17 is set low after the molten resin material 17 is injected and filled into the cavity 11, shrinkage shrinkage of the molten resin material 17 can be effectively suppressed. Can be set to a low value, the generation of residual stress at the time of consolidating the molten resin material 17 can be suppressed, and in combination with the effect of reducing the residual stress due to the decrease in the injection pressure of the molten resin material 17, the annealing treatment Omission can be further promoted, and further improvement of the effects described above can be expected.

In the method for producing a resin molded product according to the third invention of the present application, the resin molded products 2 and 3 are arranged by concentric circles of the thin strip-shaped blades 5, 5, ... Since the multi-blade impeller is formed by the manufacturing method, the blade 5 has a thin strip shape, and thus the blade 5 in the cavity 11 of the mold 10 is formed. Although the portion corresponding to is a narrow space, the molten resin material 17 can be filled into this narrow space more than enough with a low injection pressure, and the molten resin material 17 can be obtained by solidification. In the multi-blade impeller as a product to be manufactured, high-precision shape and dimension accuracy is ensured, internal residual stress is small, and time-dependent deformation is suppressed as much as possible, making it possible to omit post-treatment annealing. These synergies As a result, it is possible to provide a multi-blade impeller with high molding accuracy at a lower cost.

In the method for manufacturing a resin molded product according to the fourth invention of the present application, the molten resin material 17 in the portion of the cavity 11 corresponding to each of the blades 5, 5, ... The flow direction of the blades 5, 5, ...
Are set in the length direction of the blades 5, the blades 5, 5, ... Of the molten resin material 17 injected into the cavity 11
・ The distribution flow to the side becomes closer to the natural flow,
Therefore, the structure of the mold 10 can be simplified.
However, in the case of such a configuration, each of the above wings 5, 5,
The longer the length of .. (that is, the larger the depth of the cavity), the more the flow action of the molten resin material 17 is obstructed, and there is a concern that the molding accuracy may decrease due to insufficient filling of the resin material.

However, in the manufacturing method of the present invention, since the molten resin material 17 has high fluidity due to the addition of the fluidity promoting material, the end portions of the blades 5, 5 ,. Can be filled with the molten resin material 17, and as a result, a multi-blade impeller provided with long blades 5, 5, ... Can be provided at low cost.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for manufacturing a resin molded product according to the present invention will be described by taking a case of manufacturing a multiblade impeller 1 by injection molding as an example.

FIG. 1 is an explanatory view of a manufacturing process of a multiblade impeller 1 by the manufacturing method according to the present invention. As is apparent by comparing FIG. 1 with the process explanatory view (FIG. 6) of the conventional manufacturing method, the manufacturing method of the present invention is an essential step in the conventional manufacturing method and is a step for annealing treatment. Is omitted, or the annealing time is shortened as much as possible even if the annealing process is performed. That is, when manufacturing the multiblade impeller 1,
First, in an injection molding process 31, a molten resin material is injected into a mold 10 using an injection molding machine 12 (see FIG. 5), and a first multi-blade impeller structure which is a constituent element of the multi-blade impeller 1 is formed. The body 2, the second multiblade impeller assembly 3 and the end member 4 are respectively molded. Next, in the joining step 32, the multiblade impeller 1 is obtained by coaxially joining and integrating the respective multiblade impeller constituents 2 and 3 and the end member 4. Thereafter, without performing the annealing treatment, the rotation balance of the multiblade impeller 1 is adjusted in the balancing step 34 by using the rotation balance adjuster 23 to obtain the multiblade impeller 1 as a final product.

As described above, the manufacturing method of the present invention has the ultimate purpose of obtaining a multiblade impeller having a high shape and dimension accuracy without performing an annealing treatment when manufacturing the multiblade impeller. is there.

The first purpose of this purpose is to make the mold 1
No. 0 of the cavity 11 is filled with the molten resin material 17 to a narrow space corresponding to a blade having a thin strip shape particularly in the molding of the multiblade impeller 1. Secondly, This is realized by setting the injection pressure of the molten resin material 17 as low as possible to suppress the distortion between the resin molecules and to minimize the residual stress after solidification as much as possible. However, the above first requirement is conventionally realized by setting the injection pressure to a high pressure. Therefore, from this point, the above two requirements are contradictory. However, it is difficult to achieve both.

Therefore, in the process of attempting to develop a technique for simultaneously satisfying the above two requirements, the inventor of the present application increases the fluidity of the molten resin material to reach every corner of the cavity even if the injection pressure is lowered. Based on the idea that the molten resin material can be filled and the injection pressure is set to be low, the occurrence of residual stress can be suppressed as much as possible and the annealing process can be omitted. The fluidity promoting material having the accelerating action is added, and a gas generating agent is further adopted as the fluidity promoting material to allow the generated gas to function as a lubricant in the molten resin material to enhance the fluidity and The present invention is intended to secure the molding accuracy and further reduce the injection pressure by pressing the molten resin material against the inner surface of the cavity by the expansive force of the gas.

Specifically, the injection molding machine 12 (see FIG. 5)
A gas generating agent is added as a fluidity promoting agent to the molten resin material 17 which is melted and is injected into the cavity 11 of the mold 10, and injection molding is performed using this. The gas generating agent needs to have a property of chemically decomposing by the heat of the molten resin material 17 to generate a gas. For example, citric acid or baking soda, which is harmless to the human body, is included, and the vaporization and foaming action of these is used. Those that do are preferred.

In this way, a gas generating agent is added to the molten resin material 17 as a fluidity promoting material, and this is injected into the cavity 11 of the mold 10 to form the multiblade impeller constituent bodies 2 and 3. Thus, the following unique effects can be obtained.

In other words, when the molten resin material 17 is injected into the cavity 11 of the mold 10 by adding the gas generating agent as the fluidity promoting material to the molten resin material 17,
The gas generating agent chemically decomposes by the heat of the molten resin material 17 to generate a gas, and the gas molecules intervene between the resin molecules by their molecular motion to separate them to relax the intermolecular bond, and the resin molecules The frictional resistance between the resin molecules associated with the flow of the resin is reduced to promote the flow, and the synergistic effect of these causes the molten resin material 17 to have high fluidity. As a result, the molten resin material 1
Even if the injection pressure of 7 is set to a relatively low pressure, the molten resin material 17 is sufficiently filled in every corner of the cavity 11, and resin molded products 2 and 3 with high shape dimension accuracy can be obtained.

The multiblade impeller components 2 and 3 are
Since the injection pressure of the molten resin material 17 is low, the strain between the resin molecules during solidification of the molten resin material 17 is small, and the residual stress after solidification is also small.
Therefore, after molding each of the above multiblade impeller constituents 2 and 3,
Even when the multi-blade impeller 1 is formed by joining and integrating them with each other, the residual stress of the multi-blade impeller 1 is small, and even if it is not annealed, it is hardly deformed with time. The processing time can be made extremely short, and the multiblade impeller 1 can be provided at a lower cost.

Further, by using the gas generating agent as the fluidity promoting material, the molten resin material 17 injected and filled in the cavity 11 by the expansion force of the gas generated from the gas generating agent flows from the inside to the inside surface of the cavity. It is pressed. Therefore, even if the holding pressure for the molten resin material 17 after injection-filling the molten resin material 17 into the cavity 11 is set low, shrinkage shrinkage of the molten resin material 17 can be effectively suppressed, and as a result, As much as the holding pressure can be set low, the generation of residual stress at the time of consolidating the molten resin material 17 can be suppressed.
Combined with the effect of reducing the residual stress due to the reduction of the injection pressure of No. 7, the omission of the annealing process is further promoted.

Further, the fact that the injection pressure of the molten resin material 17 can be set low means that the injection molding machine 12 can be made smaller and the die 10 can be downsized by lowering the mold clamping pressure. This can contribute to the reduction of equipment costs.

Further, since the molten resin material 17 has a high fluidity due to the addition of the fluidity promoting material, when the multi-blade impeller constituents 2 and 3 are molded, the multi-blade impeller constituents are formed. Set the length of each wing 5, 5, ...
Even if the space of the cavity 11 corresponding to each of the blades 5, 5, ... Is a narrow space having a small thickness and a long depth, the molten resin material 17 is sufficiently filled up to every corner of the narrow space. Can be made. That is, it is possible to easily obtain the multiblade impeller constituents 2 and 3 having the blades 5 having a length longer than the conventional one.

Due to the fact that it is possible to obtain the multiblade impeller components 2 and 3 having the blades 5 having a large length,
The following additional effects can be obtained.

That is, the fact that the length of the blade 5 can be increased means that the axial length of each of the above-mentioned multiblade impeller constituents 2 and 3 can be increased, and accordingly, each of these multiblade impeller constituents 2 and 3 can be increased. In the multiblade impeller 1 configured by connecting in the axial direction, when the axial lengths of the multiblade impeller 1 and the multiblade impeller constituents 2 and 3 are long, the assembling is performed. Since the number of the multiblade impellers 1 can be reduced, the number of joints between the multiblade impeller constituents 2 and 3 at the time of manufacturing the multiblade impeller 1 is reduced.
The manufacturing cost can be reduced.

In addition, the fact that the number of the multiblade impeller constituents 2 and 3 constituting the multiblade impeller 1 is reduced means that the multiblade impeller constituents 2 can be viewed as the multiblade impeller 1 as a whole. That is, the number of the end plates 6 and 7 provided on the first and third terminals is reduced. Here, the end plates 6 and 7 exist so as to divide the multiblade impeller 1 in the axial direction thereof, and are one of the factors that lower the air blowing performance of the multiblade impeller 1. Since the number of the end plates 6 and 7 is reduced, the multi-blade impeller 1 can be expected to have improved air blowing performance.

[Brief description of drawings]

FIG. 1 is an explanatory view of a manufacturing process in a method for manufacturing a resin molded product according to the present invention.

FIG. 2 is a perspective view of a multiblade impeller.

FIG. 3 is an exploded perspective view showing a configuration of a multiblade impeller.

FIG. 4 is a perspective view showing a blade structure of a multi-blade impeller.

FIG. 5 is a schematic diagram of an overall configuration of an injection molding device.

FIG. 6 is a drawing explaining the manufacturing process of the multiblade impeller.

[Explanation of symbols]

1 is a multi-blade impeller, 2 is a first impeller structure, 3 is a second impeller structure, 4 is an end member, 5 is a blade, 6 is an end plate, 10 is a mold, 11 is a cavity, 12 is Injection molding machine, 13 melt extrusion section, 14 injection nozzle, 15 hopper, 16 resin material, 17 molten resin material, 21 ultrasonic bonding machine, 22
Is an annealing furnace, 23 is a rotation balance adjuster, 31 is an injection molding step, 32 is a joining step, and 33 is an annealing step.

Claims (4)

[Claims] 1. The molten resin material (17) is added to the molten resin material (1).
7) A fluidity promoting material for promoting fluidity is added, and this is injected into the cavity (11) of the mold (10) to produce resin molded products (2), (3). Manufacturing method of resin molded product. 2. The method for producing a resin molded article according to claim 1, wherein a gas generating agent that chemically decomposes by heating to generate a gas is used as the fluidity promoting material. 3. The resin molded article (2), (3) according to claim 1 or 2, wherein the thin strip-shaped blades (5), (5), ... Are arranged in parallel on a concentric circle at predetermined intervals. A method for producing a resin molded product, which is a multi-blade impeller having the following structure. 4. The blades (5), (5), ... Of the cavity (11) according to claim 3,
The flow direction of the molten resin material (17) in the portion corresponding to the is set to the length direction of the blades (5), (5) ,.