JP3098315B2 - Plastic moldings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic molded article applied to hinges, gears, desk lamps and the like 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 a lid with a display screen is attached via a hinge on the opposite side, and the lid is turned half a turn so that the display screen faces the operation side. Has become. The display screen is
When viewed from the front of the operation side, it is desirable that the lid be stopped at an arbitrary position in terms of rotational movement of the display screen from the viewpoint of usability such that disturbance light is reflected on the surface glass plate and becomes difficult to see. In view of such circumstances, a hinge with a torque function has been proposed in which a display screen can be stopped at an arbitrary position by adding a rotation torque function to the hinge.

[0003] As an injection molding method for molding a hinge having a torque function, a primary member is inserted into a mold, a secondary member is filled in the mold, and the primary side material is shrunk by the molding shrinkage force of the secondary material. Some devices generate a tightening force on a material to make the primary member rotatable or slidable with respect to the secondary member. In this example, when resin is used as the material of the insert side (primary side) when performing injection molding, the resin on the secondary side to be molded and injected is resistant to heat and pressure and is incompatible. That is good. If such a condition is satisfied, the primary member, for example, the shaft becomes rotatable or slidable with respect to the secondary member, for example, the bearing.

[0004]

However, in the case of injection molding, when various resins are actually combined and molded, the interface between the insert side and the injected resin is not molten, but the heat generated during molding is high. Due to the pressure and pressure, the resin injected into the member on the insert side comes into close contact, and the starting force is high, so that there is a disadvantage that it cannot be commercialized as it is.

[0005] As measures to solve the problem, fluorine, silicone oil or the like is applied to the surface of the insert-side member to improve the adhesion, or after the secondary molding, the coating agent adhering to portions other than the sliding portion is washed with a Freon liquid. A step was required, and a step of releasing the starting force by running-in after molding was required.

SUMMARY OF THE INVENTION An object of the present invention is to omit a coating agent application step for improving the adhesion between a molded member on the primary side and a molded member on the secondary side after molding, and to eliminate a cleaning step using a chlorofluorocarbon liquid which is a source of air pollution. Another object of the present invention is to eliminate the running-in operation between the primary molding member and the secondary molding member.

[0007]

The fine structure of a polyester liquid crystal polymer such as Vectra (trade name: Celanese Corporation) is called an extended molecular chain structure as shown in FIG. It is very different from the structure, and the molecular chain is hard to bend even in the molten state and keeps a rod shape, so there is little entanglement of molecules during melting, and it is oriented in the flow direction by receiving only a small shear stress during molding, especially The skin layer on the surface of the molded article is called fibril, and has a unique surface structure in the form of fine fibers which are extremely inert chemically. The characteristic of this structure is that it is extremely poorly compatible with ordinary polymer plastics. As a result, even in the same molded article, the mechanical strength at the portion where the skin layers are joined like the weld portion is weak, and is often pointed out as a disadvantage of this liquid crystal polymer.

In the present invention, the disadvantage of such a liquid crystal polymer is used as an advantage. The present invention combines a primary molding member and a secondary molding member, and the secondary molding member generates a movable clamping force on the primary molding member by the molding contraction force. Things. As the primary molding member, a polyester liquid crystal polymer is used. This polyester-based liquid crystal polymer exhibits a characteristic skin layer property with respect to other resins, has no compatibility, has low adhesion, and has a very small difference in starting force from that at the time of use torque. For this reason, it is possible to omit the steps of releasing the starting force by the above-described running-in operation and applying a coating agent for preventing adhesion, and to eliminate the necessity of the air pollution source Freon liquid.

The secondary molded member is preferably made of a material having a large molding shrinkage in order to generate a torque on the primary molded member. In addition, after molding, a material whose tightening force (force for holding the insert member) by softening due to water absorption or the like is unlikely to cause stress relaxation due to creep may be selected. Therefore, from the viewpoint of high molding shrinkage, a resin having a low water absorption may be selected from crystalline resins. What is necessary is just to adjust from a shrinkage rate by the torque required of a secondary side molding member.
That is, when a large torque is required, a material having a relatively large shrinkage ratio such as polyacetal may be selected. When a medium torque is required, a material having a relatively small shrinkage ratio such as polybutylene terephthalate may be selected. For a demand for a smaller torque, a material having a relatively small shrinkage ratio such as 12 nylon may be selected.

[0010] If necessary, a silicone oil, molybdenum sulfide, fluorine number, or the like may be mixed in the molded members on the primary side and the secondary side, respectively, if necessary. As a reinforcing method, carbon fiber, glass fiber, calcium whisker, graphite whisker, or the like may be mixed.

The scope of the present invention is not limited to hinges of OA equipment, but also includes, for example, a gear composed of a gear main body and a shaft slidable in the axial direction on the main body, and an arm stand capable of tilting with respect to a table. A desk lamp and the like are included.

The method for producing a plastic molded article of the present invention is as follows.
After fixing the primary-side molded member in the molding die, the secondary-side molded member is molded, and a tightening force is generated in the primary-side molded member by the molding contraction force, and the primary or secondary side is formed. The torque function is added to the operation such as the rotation of the molded member.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, a case where the present invention is applied to a hinge of a foldable lid having a display screen of a personal computer will be described with reference to FIGS. 1 to 3, the hinge is a combination of a rotating shaft 1 as a primary molding member and a bearing 2 as a secondary molding member that supports the rotating shaft. The rotating shaft 1 is made of a polyester-based liquid crystal polymer, and has rotating projections 1b and 1c integrally formed on both sides of an intermediate portion positioning 1a. The rotating projections 1b and 1c are formed in the shape of an abacus ball in cross section.
They are adjacent to each other at a predetermined interval.

The bearing 2 is made of a crystalline resin and has bearing portions 2a, 2a, respectively. The bearing portion 2a
It covers the rotating projections 1b and 1c. The bearing 2a is rotated by the molding shrinkage force generated during the injection molding of the bearing.
A torque function is added to the rotation of the rotating projection by generating a tightening force at the point c. The mechanism of torque generation is as described later.

As shown in FIG. 4, the bearing 2 is fixed to the main body 3. The rotating shaft 1 is connected to a lid 4 that also serves as a display. A keyboard 5 is provided on the front side of the main body 3.

Next, a method of manufacturing the hinge will be described. As shown in FIG. 5, the injection molding die 6 is molded by inserting and fixing a preformed rotary shaft 1 in a cavity and filling the cavity with a liquid synthetic resin 7.
Numeral 8 is a gap generated by shrinkage of the synthetic resin.

The shrinking force of the synthetic resin 7 tightens the inclined surfaces 1b1 and 1c1 of the rotating projections 1b and 1c in the direction of the arrow in FIG. As a result, friction is generated on the slopes 11b1 and 11c1 with respect to the rotation of the rotating shaft 1 due to the tightening force, and a torque function is added. This is the mechanism of torque generation.

In the above example, the shaft may be fixed and the bearing may be rotatable.

[0019]

According to the present invention, since the polyester-based liquid crystal polymer is used for the primary molded member and the crystalline resin is used for the secondary molded member, the primary molded member and the secondary molded member after molding are used. It is possible to improve the adhesion to the member, eliminate the coating agent application process for improving the above-mentioned adhesion, and eliminate the need for a cleaning process using Freon liquid, which is a source of air pollution. The running-in operation with the side forming member can be eliminated.

[Brief description of the drawings]

FIG. 1 is a partially sectional perspective view showing one embodiment of the present invention.

FIG. 2 is a perspective view of a rotating shaft.

FIG. 3 is a sectional view of a main part.

FIG. 4 is a perspective view adapted to a notebook computer.

FIG. 5 is an enlarged sectional view showing one step of molding.

FIG. 6 is a diagram showing the microstructure of a liquid crystal polymer and a general polymer plastic.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary molding member (rotary shaft) 1b Rotating protrusion 1c Rotating projection 2 Secondary molding member (bearing) 2a Bearing part

Claims (1)

(57) [Claims] 1. A primary molding member using a polyester-based liquid crystal polymer and a secondary molding member using a crystalline resin are combined, and the secondary molding member is formed by the molding shrinkage force of the primary molding member. A plastic molded product wherein a movable clamping force is generated on a side molding member.