JPH10217278A - Production of bearing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a bearing structure possible to rotate and impossible to escape by a series of molding processes and to achieve the reduction of production cost and wt. reduction. SOLUTION: An oxyalkylene group-containing polyvinyl alcohol resin is injected to mold a temporary shaft having a large diameter part 3a to a part to be born and the part to be born of the temporary shaft is inserted to inject an aromatic polyester liquid crystal polymer to mold a bearing part 2 and this bearing part 2 is heated in hot water to elute the temporary shaft in hot water and this bearing part 2 is inserted to inject a polyacetal resin to mold a shaft and a bearing structure A wherein the shaft 3 is born in a freely rotatable manner by the bearing part 2 by molding contraction force at a time of the molding of the shaft 3 is molded.

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 bearing structure applied to, for example, an opening / closing lid of a portable personal computer or a word processor.

[0002]

2. Description of the Related Art Portable so-called OA (office automation) devices, such as personal computers (PCs), word processors, printers, etc., are often provided with foldable lids due to their portability. For example, in a notebook computer, a keyboard or the like is arranged on the near side, and the opposite side is a lid with a display screen, both are attached via hinges, the lid is turned half a turn, and the display screen is displayed on the operation side. It is facing. As the structure of the hinge, the bearing portion and the shaft are formed respectively, the bearing portion is fixed to the operation side, the shaft is fixed to the lid portion, and the shaft is rotatably and undetachably mounted on the bearing portion. I have. A metal spring mechanism is usually used for the structure of this hinge, and a washer or the like is fixed to an end of the shaft to prevent escape.

However, in such a manufacturing method in which such a bearing structure is molded and assembled for each part as described above, the number of manufacturing steps increases, and since the parts must be assembled after they have been molded, the number of steps increases. And complicated. In addition, there are many problems such as the disadvantage of using a metal spring mechanism for weight reduction.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems and to manufacture a rotatable and non-removable bearing structure by a series of molding steps. Therefore, it is an object of the present invention to significantly reduce the manufacturing cost by manufacturing with a small number of processes without the assembling process, and to achieve a reduction in cost and weight without using a metal spring.

[0005]

In order to achieve the above-mentioned object, the present invention provides an oxyalkylene having a cavity having a large-diameter portion in a part of a bearing portion. A primary molding step of injecting a group-containing polyvinyl alcohol-based resin to form a provisional shaft, and inserting a portion of the provisional shaft that is to be bearing into a cavity having a shape matching the outer shape of the bearing portion; A second molding step of injecting the aromatic polyester liquid crystal polymer into the bearing portion where the bearing portion of the temporary shaft is inserted, and the bearing portion of the temporary shaft is inserted. An elution step of heating the bearing portion in the hot water to elute the temporary shaft into the hot water, and a bearing after the elution step in a cavity having a shape matching the outer shape of the shaft in a state of being supported by the bearing portion. In part And over DOO, by injecting the polyacetal resin into the cavity, the shaft at its molding shrinkage force and a tertiary forming step of forming a bearing structure which is rotatably bearing in the bearing unit.

[0006] Since the provisional shaft formed in the first molding step is eluted in the elution step after the second molding step, it has a lower melting point than that of the plastic material from which the bearing is to be molded, and is water soluble. It is desirable to use a material which can be easily eluted due to its properties. The oxyalkylene group-containing polyvinyl alcohol-based resin used in the present invention is, for example, trade name “Ecomaty AX” manufactured by Nippon Synthetic Chemical Industry Co., Ltd. and is suitable for injection molding because it has excellent melt moldability. Since it has a melting point of 190-200 ° C. and is water-soluble, it is suitable for the elution step, and since it is biodegradable, it is extremely desirable in that it is naturally reduced without polluting the environment.

It is necessary that the bearing portion of the temporary shaft formed by the secondary forming step into which the bearing portion is inserted can be formed without melting the temporary shaft. Further, the bearing structure is desirably a highly heat-resistant thermoplastic resin, and is preferably an aromatic polyester liquid crystal polymer (hereinafter, referred to as “liquid crystal polymer”).

Therefore, in the present invention, the use of a liquid crystal polymer in the second molding step was considered. However, the problem here is that the melting point of the polyvinyl alcohol-based resin serving as the tentative axis is far from 190 to 200 ° C. Resin temperature above 29
Due to the injection at 0 to 350 ° C., the surface of the temporary shaft is fused, deformed, or fused with the liquid crystal polymer, and as a result, it is expected that a precise shape cannot be obtained as a secondary molded product. It was to have been.

However, as a result of various experiments by the present inventors,
Melting, deformation and fusion were not found contrary to such a prediction, and it was found that the method was sufficiently practical. Although this is an inference, the liquid crystal polymer exhibits crystalline properties while in a molten state, further exhibits an elongated molecular structure in the flow direction during molding, and its surface exhibits a unique structure called a skin layer. In addition, since the cooling and solidifying speed is much faster than that of a general resin and the fluidity is very high, the injection filling speed is high. It seems to be a unique interaction generated from the result of such a combination.

The present inventor paid attention to this point and decided to use this liquid crystal polymer in the secondary molding step, so that the inserted temporary shaft could be molded without melting and deforming, and a precise injection molded product could be obtained. It is very desirable in that it is excellent in the production and also in the step of dissolving the inserted temporary axis after the secondary molding step, because of the excellent releasability from the temporary axis due to the presence of the skin layer.

Further, since the elution step is carried out in hot water to elute the tentative axis, the elution is not only easy, but also "Ecomaty AX" is naturally degraded without polluting the environment due to its biodegradability. It is very desirable because it can.

The tertiary forming step is a step of forming a shaft to be bearing on the bearing portion. It is necessary that the shaft can be formed without melting and deforming the bearing portion and without fusing to the bearing portion. It is. The polyacetal resin used in the third molding step is a crystalline material, and the molding temperature is lower than that of the liquid crystal polymer.
It can be molded without deformation and fusion, and the molding shrinkage force is larger than other resins, and a sufficient gap can be created between the bearing and the molded part. And smooth rotation becomes possible. Furthermore, it is extremely desirable as a rotating shaft in that it is strong and has sufficient mechanical strength.

The large-diameter portion of the shaft has a trapezoidal or chevron-shaped cross section, which produces a substantially uniform gap between the shaft and the bearing.
This is preferable in that the shaft rotates smoothly in the bearing.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A bearing structure A according to the present invention is shown in FIG.
Will be described in detail for each of the steps shown in FIGS.

Embodiment 1 (a) As a first step, FIG. 1 shows a temporary shaft 1 which is formed by a first forming step. The temporary shaft 1 is provided with an oxyalkylene group-containing polyvinyl alcohol-based resin (trade name “Ecomaty AX” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) in a cavity (not shown) formed on the opposing surfaces of the normal upper and lower molds. ) (Hereinafter simply referred to as “ecology”) at a predetermined injection pressure and molded. The shape of the cavity matches the outer shape of the shaft having the large-diameter portion 1a in a part of the bearing. The large diameter portion 1a has a trapezoidal cross section in this example. An example of the injection molding conditions is as follows.

"Ecomaty" is injected at a cylinder temperature of 210 ° C., a mold temperature of 25 ° C., an injection pressure of 900 kg / cm ² , and a cooling time of 20 seconds.

(B) Next, as a second step, FIG. 2 shows a bearing portion 2 into which a bearing portion of the temporary shaft 1 (near the large-diameter portion 1a) is inserted. It is formed by the process. The bearing 2 has a cavity (not shown) having a shape conforming to the outer shape of the bearing formed on the opposing surfaces of the normal upper and lower molds. Then, a liquid crystal polymer (grade C810 of trade name “VECTRA” manufactured by Polyplastics Co., Ltd.) is placed in the cavity around the temporary shaft 1.
(Hereinafter simply referred to as "Vectra") at a predetermined injection pressure. An example of the injection molding conditions is shown below.

Vectra with a cylinder temperature of 320 ° C., a mold temperature of 110 ° C., and an injection pressure of 1200 kg / cm ^2.
And the cooling time is 15 seconds.

(C) Next, as a third step, an elution step of eluting the provisional axis 1 will be described with reference to FIG. The bearing portion 2 in which the temporary shaft 1 formed in the second forming step is inserted is put in hot water and heated to 80 to 100 ° C. Since the liquid crystal polymer has a heat deformation temperature of 200 ° C. or more, “Ecomaty” can be eluted in hot water by heating to 80 to 100 ° C., but it gives no change to the liquid crystal polymer. As shown in FIG. 3, the bearing 2 has a through-hole 2a having a shape corresponding to the inserted temporary shaft 1.

(D) Next, as a fourth step, FIG. 4 shows a bearing structure A in which a shaft is rotatably supported by the bearing part 2, and this is formed by a third forming step. Things. In this bearing structure A, although not shown, a cavity having a shape conforming to the external shape of a state in which the shaft is supported by the bearing portion is formed on the opposing surfaces of the normal upper and lower molds, and FIG. The bearing 2 after the elution step shown is inserted, and a polyacetal resin (trade name “Duracon” M90 manufactured by Polyplastics Co., Ltd.) (hereinafter simply referred to as “Duracon”) is inserted into the cavity around the bearing 2. The shaft 3 is formed by injection at an injection pressure of
An example of the injection molding conditions is shown below.

“Duracon” is injected at a cylinder temperature of 190 ° C., a mold temperature of 80 ° C., an injection pressure of 1200 kg / cm ² , and a cooling time of 20 seconds.

The formed shaft 3 has a large-diameter portion 3a formed in a part of the bearing, similarly to the provisional shaft 1, so that it cannot escape from the bearing portion 2. Also, between the bearing portion 2 made of the liquid crystal polymer at the time of the second molding and the shaft 3 made of the polyacetal resin at the time of the third molding, both the radial direction and the length direction contract due to the molding shrinkage force of the shaft 3. Since a gap g is generated between the through-hole 2a and the inner peripheral surface of the through-hole 2a, the shaft 3 can rotate smoothly in the bearing 2.

FIG. 5 shows an example of a bearing structure manufactured by such a manufacturing method. The bearing structure is such that both ends of a shaft 3 are used as bearings, and each of the shafts 3 is supported by a bearing 2. ing. The left and right bearings 2, 2 are substrates 2
b, and the board has left and right bearings 2,
A spring portion 2c is provided so that the interval between the two can be finely adjusted. A mounting hole 2d is formed in each substrate with the spring portion 2c interposed therebetween.
2d is formed.

As shown in FIG. 6, in addition to the large diameter portions 3a, 3a being formed at the bearing portions at both ends of the shaft 3, the shaft 3 is disposed between the bearing portions 2 in the left-right direction. The positioning projection 3b which regulates the displacement of is formed.

Embodiment 2 The shape of the large diameter portion 3a of the shaft 3 is not limited to a trapezoid. According to the embodiment shown in FIG. 7, the large diameter portion of the shaft 30 forms a chevron 30 a, and the through hole 20 a of the bearing portion 20.
Needless to say, the shape of the shape also corresponds to this chevron. In this case, the same operation and effect as those of the above embodiment can be obtained.

[0026]

The present invention uses a polyvinyl alcohol resin containing an oxyalkylene group for the material of the temporary shaft and an aromatic polyester liquid crystal polymer for the material of the bearing portion, so that the bearing can be melted without melting the temporary shaft. The part can be molded.
Since a strong alignment layer in the flow direction is formed on the surface of the liquid crystal polymer, it has excellent release properties from the temporary axis and hardly generates burrs, and it has excellent heat resistance, so the temporary axis can be safely eluted. . Since the temporary axis is eluted in hot water, it is not only easy to elute, but also excellent in that this material is biodegradable and can be naturally reduced without polluting the environment. The shaft is molded from polyacetal resin by inserting the bearing after the temporary shaft is eluted, so the shaft contracts due to the molding shrinkage force when the shaft is molded, so that the shaft rotates smoothly between the shaft and the bearing. A sufficient gap can be formed. In this manufacturing method, the assembly of the shaft and the bearing portion is not required, and the entire structure can be formed by a series of flow using synthetic resin, so that the cost can be reduced and the weight can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view showing a temporary shaft formed by a first step of the manufacturing method of the present invention.

FIG. 2 is a cross-sectional view showing a bearing unit into which a temporary shaft formed in a second step is inserted.

FIG. 3 is a cross-sectional view showing a bearing portion after a dissolution step as a third step.

FIG. 4 is a sectional view showing a bearing structure manufactured by a fourth step.

FIG. 5 is a partially cutaway perspective view showing the entire bearing structure.

FIG. 6 is a perspective view showing the entire shaft of FIG. 5;

FIG. 7 is a sectional view showing another example of the bearing structure.

[Explanation of symbols]

 A Bearing structure 1 Temporary shaft 2, 20 Bearing part 3, 30 Shaft 3a, 30a Large diameter part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B29K 29:00 59:00 B29L 31:34

Claims (3)

[Claims] An oxyalkylene group-containing polyvinyl alcohol-based resin is injected into a cavity having a shape that matches the outer shape of a shaft having a large diameter portion in a part of a bearing portion to form a temporary shaft. Primary molding step, insert the bearing portion of the temporary shaft into a cavity having a shape matching the outer shape of the bearing portion, and inject an aromatic polyester liquid crystal polymer into the cavity,
A secondary forming step of forming a bearing portion in which the bearing portion of the temporary shaft is inserted; and heating the bearing portion in which the bearing portion of the temporary shaft is inserted in hot water in the temporary shaft. The bearing after the above-mentioned elution step is inserted into a cavity having a shape conforming to the outer shape of the state in which the shaft is supported by the bearing, and a polyacetal resin is filled in the cavity. Injecting and molding a bearing structure in which the shaft is rotatably supported on the bearing portion by the molding contraction force. 2. The large-diameter portion of the shaft according to claim 1,
A method for producing a bearing structure, wherein the cross-sectional shape is trapezoidal. 3. The large diameter portion of the shaft according to claim 1,
A method for producing a bearing structure, wherein the cross-sectional shape is a mountain shape.