JPH1092635A - Intermediate product of integral arm used for actuator of disk device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an integral arm having a plurality of arms formed with high dimensional accuracy. SOLUTION: A primary gate and a secondary gate are respectively provided between a spool 6 and/or runner and at least one connecting section 3 which is connected with the arms 1 of an integral arm section 2 and between the connecting section 3 and the arms 1 of the section 2 and a molten resin is made to flow to the connecting section 3 from the spool section 6 through the primary gate and, then, to each arm 1 through the secondary arm from the connecting section 3. An intermediate product taken out from the mold is solidified while the connecting section 3 is attached to the product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate product of an integrated arm which is used for a fixed magnetic disk drive or the like and which can be used for a swing type actuator for driving a magnetic head along a circular orbit, and a method of manufacturing the integrated arm. About.

[0002]

2. Description of the Related Art Conventionally, an integrated arm portion integrally having a plurality of arms used for an actuator of a disk drive, and at least one connecting portion which connects the plurality of arms and is finally removed is provided. As an integrated arm intermediate product provided, there is an application filed with Japanese Patent Application No. 7-169356.

[0003] Specifically, in this intermediate product, a sprue or a runner at the time of injection molding is used as a connecting portion thereof. In other words, when injection is performed from the tips of a plurality of arms, the sprue or runner inevitably connects the plurality of arms when the molded body is released. The arms are connected.),
Even after releasing the molded body, without disconnecting the sprue and runner, at least until it is sufficiently solidified, as a connecting member,
It is to remain connected. According to this,
Since the connecting part is fully solidified while being connected to each arm, the connecting part functions to fix the tip of each arm during the solidification process, stabilize the dimensions, and maintain the parallelism between the arms. Therefore, an integrated arm obtained by separating the connecting portion is expected to have high dimensional accuracy.

In general, sprues, runners, gates, and the like are names of respective functional portions in a mold, and may also indicate a resin solidified at each portion. Here, as long as there is no risk of confusion, it is used in any meaning as appropriate without notice. Similarly, a cavity portion for forming a connecting portion or an arm is simply referred to as a connecting portion or an arm.

[0005]

However, when the sprue or the runner is used as the connecting portion as described above, such a connecting portion has the following instability factors which cannot be avoided in injection molding.

First, the resin in the sprue or the runner is continuous (coupled) with the molten resin in the tip of the nozzle of the molding machine even in the step of solidifying the molded article by injection molding. Therefore, the resin in the sprue or the runner continues to receive a slight pressure fluctuation due to the fluctuation of the screw position, and the pressure in the system is not constant, and thus the specific volume is not constant.

Second, as described above, the resin in the sprue or the runner is continuously (coupled) with the molten resin in the tip of the nozzle of the molding machine even in the step of solidifying the molded article by injection molding.
This part is usually not sealed after injection and filling. Therefore, in the sprue and the runner, a phenomenon that a dimensional change occurs due to the elastic recovery of the molten resin at the same time when the screw retreat starts (retaining the pressure) is observed.

Third, sprues and runners are usually designed to have a larger diameter than a gate or the like in order to reduce pressure loss during injection / filling. Relatively slow, dimensional changes are likely to occur due to elastic recovery when the mold is released.

In short, in the above-mentioned application, it is expected that the sprue and the runner are solidified so that their shapes do not change thereafter when the mold is released. Is in contact with the injection nozzle and it is difficult to block the injection nozzle, so it is difficult to solidify the sprue or runner to some extent before releasing. Furthermore, since sprues and runners are affected by pressure fluctuations such as pressure holding, pressure holding release, and mold release, dimensions are already unstable at the time of mold release, and dimensions change after release. Cheap. Therefore, the arms connected by sprues or runners will instead
The arm dimensions such as the arm length tend to fluctuate. This is a problem for an integrated arm that requires precise molding.

SUMMARY OF THE INVENTION An object of the present invention is to provide an intermediate product of an integrated arm and an injection molding method of the integrated arm, which can provide an integrated arm with higher dimensional accuracy in view of the problems of the prior art. is there.

[0011]

In order to achieve this object, an integrated arm intermediate product according to the present invention comprises an integrated arm having a sprue and / or runner and a plurality of arms used in a disk drive actuator. Part and
At least one connection that connects and ultimately removes the plurality of arms, a primary gate that is between the sprue and / or runner and the connection, the connection and the integrated arm And a secondary gate existing between the plurality of arms of the portion. Here, the term "sprue and / or runner" includes those having a sprue and a runner, and those having no distinction between a sprue and a runner.

In a more specific and preferred embodiment, the secondary gate is connected to a tip of each arm. Further, the connecting portion extends in a direction perpendicular to each arm, and has a columnar shape having a length equal to or longer than at least the distance between the arms at both ends, or has a thickness similar to the thickness of each arm. Characterized by having a cylindrical shape.

[0013] The primary gate is provided with the sprue and / or extending in parallel with the connecting portion in the axial direction.
Or a film gate connecting the runner and the connecting portion, extending substantially in the axial direction over the length of the connecting portion, or the sprue extending in parallel with the connecting portion in the axial direction. And / or the same number of gates as the number of the arms, connecting the runner and the connecting portion at substantially the same position as each arm when viewed in the axial direction;
Alternatively, it is a gate for connecting the sprue and / or runner extending in the axial direction in series with the connecting portion and one end of the connecting portion.

Further, the thickness d of the secondary gate has a relationship of 0.9D <d with the thickness D of the arm to which the secondary gate is connected. By doing this,
When the molten resin flows into the mold, it is possible to suppress so-called jetting phenomenon from occurring.

On the other hand, the injection molding method for an integral arm according to the present invention is a method for injection molding of an integral arm integrally having a plurality of arms used for an actuator of a disk drive. The molten resin is caused to flow into a connecting part connecting the plurality of arms through a gate, and then the molten resin is flowed into each arm from the connecting part through a secondary gate.

In this case, after the inflow resin is solidified, an intermediate product including the sprue and / or runner, the primary gate, the connecting portion, the secondary gate, and the plurality of arms is taken out of the mold, or the mold is further removed. Annealing the intermediate product itself taken out of the mold, or the integrated arm having at least the connecting part except for the sprue and / or runner or the sprue and / or runner and the primary gate from the intermediate product, The method is characterized in that a connection is made between a secondary gate and the arm.

As the thermoplastic resin, it is difficult to deform when the rigidity after solidification is high, so that the flexural modulus is 8 × 10 ² kgf.
/ Mm ² (according to ASTM D790), that is, so-called engineering plastic is preferably used. For example, polyamide resins such as nylon; polyacetal resins; polycarbonate resins; modified polyphenylene ethers; polyester resins such as polyethylene phthalate and polybutylene phthalate; polyphenylene sulfide resins; polysulfone resins; Ether ketone resin;
Wholly aromatic polyester resin such as polyarylate; AB
S-based resin; polyolefin-based resin such as reinforced polypropylene; thermotropic liquid crystal polymer;

Preferred as the thermotropic liquid crystal polymer is a resin which exhibits optical anisotropy in a molten state and is thermoplastically meltable. Such a polymer exhibiting optical anisotropy at the time of melting has a property that the polymer molecular chains take a regular parallel arrangement in a molten state. The properties of the optically anisotropic molten phase can be confirmed by a normal polarization inspection method using an orthogonal polarizer. Polymers that do not show general melt anisotropy are isotropic in the molten state,
When anisotropy is exhibited in the melting process, the phase changes from a solid phase to an isotropic phase via an anisotropic liquid crystal phase. In addition, mechanical anisotropy can be confirmed. That is, when injection molding is performed, peeling and fibrillation of the surface of the molded article become remarkable, and the difference in physical properties between the direction of flow of the resin and the direction perpendicular to the direction can be confirmed.

The resin exhibiting optical anisotropy in the molten state is generally known as a thermotropic liquid crystal polymer. The thermotropic liquid crystal polymer is generally made from monomers that are elongated, flat, and rigid along the long chain of the molecule and have multiple chain extension bonds in either a coaxial or parallel relationship. .

The polymer exhibiting optical anisotropy when melted is
It exhibits the property that the polymer molecular chains adopt a regular parallel arrangement in the molten state. The properties of the optically anisotropic molten phase can be confirmed by a usual polarization inspection method using a crossed polarizer.

Preferred as the above-mentioned thermotropic liquid crystal polymer are thermotropic liquid crystal polyesters, for example, liquid crystalline polyesters, liquid crystalline polyesterimides, and more specifically, (wholly) aromatic polyesters,
Polyester amide, polyester carbonate and the like. It is included in the category of polyester as long as it contains a plurality of polyester bonds in the molecule. Further preferred polyesters are aromatic polyesters.

In the thermotropic liquid crystalline polyester which can be used in the present invention, a part of one polymer chain is composed of a polymer segment forming an anisotropic molten phase, and the remaining part forms an anisotropic molten phase. Polymers composed of non-polymer segments are also included. Further, a composite of a plurality of thermotropic liquid crystal polymers is also included.

Representative examples of the monomers constituting the thermotropic liquid crystal polyester include (a) at least one kind of aromatic dicarboxylic acid, (b) at least one kind of aromatic hydroxycarboxylic acid compound, and (c) aromatic diol. (D) (d1) aromatic dithiol, (d2) aromatic thiophenol, (d3) at least one aromatic thiol carboxylic acid compound, (e)
At least one of aromatic hydroxyamines and aromatic diamine compounds is exemplified.

Although these may be constituted independently,
Many are (a) and (c), (a) and (d), (a),
(B) and (c), (a), (b) and (e), or (a), (b), (c) and (e), and the like.

The aromatic dicarboxylic acid compound (a) includes terephthalic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-triphenyldicarboxylic acid, 2,6
-Naphthylene dicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, diphenoxybutane
4,4'-dicarboxylic acid, diphenylethane-4,4 '
-Dicarboxylic acid, isophthalic acid, diphenyl ether-
3,3'-dicarboxylic acid, diphenoxyethane-3,3
Aromatic dicarboxylic acids such as' -dicarboxylic acid, diphenylethane-3,3'-dicarboxylic acid, 1,6-naphthalenedicarboxylic acid or chloroterephthalic acid, dichloroterephthalic acid, bromoterephthalic acid, methylterephthalic acid, dimethylterephthalic acid, Alkyl, alkoxy or halogen-substituted aromatic dicarboxylic acids such as ethyl terephthalic acid, methoxy terephthalic acid and ethoxy terephthalic acid are mentioned.

Examples of the aromatic hydroxycarboxylic acid compound (b) include 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 6-hydroxy-1-naphthoic acid. Hydroxycarboxylic acid or 3-methyl-4-hydroxybenzoic acid, 3,
5-dimethyl-4-hydroxybenzoic acid, 2,6-dimethyl-4-hydroxybenzoic acid, 3-methoxy-4-hydroxybenzoic acid, 3,5-dimethoxy-4-hydroxybenzoic acid, 6-hydroxy-5 Methyl-2-naphthoic acid, 6-hydroxy-5-methoxy-2-naphthoic acid, 2-chloro-4-hydroxybenzoic acid, 3-chloro-4-hydroxybenzoic acid, 2,3-dichloro-4-hydroxybenzoic acid Acid, 3,5-dichloro-4-hydroxybenzoic acid, 2,5-dichloro-4-hydroxybenzoic acid, 3-bromo-4-hydroxybenzoic acid, 6-hydroxy-5-chloro-2-naphthoic acid, 6 -Hydroxy-
7-chloro-2-naphthoic acid, 6-hydroxy-5,7
And alkyl-, alkoxy-, or halogen-substituted aromatic hydroxycarboxylic acids such as -dichloro-2-naphthoic acid.

As the aromatic diol (c),
4'-dihydroxydiphenyl, 3,3'-dihydroxydiphenyl, 4,4'-dihydroxytriphenyl,
Hydroquinone, resorcinol, 2,6-naphthalenediol, 4,4'-dihydroxydiphenylether, bis (4-hydroxyphenoxy) ethane, 3,3'-dihydroxydiphenylether, 1,6-naphthalenediol, 2, Aromatic diols such as 2-bis (4-hydroxyphenyl) propane and bis (4-hydroxyphenyl) methane or chlorohydroquinone, methylhydroquinone, t-butylhydroquinone, phenylhydroquinone, methoxyhydroquinone, phenoxyhydroquinone, 4-chloro Alkyl, alkoxy or halogen-substituted aromatic diols such as resorcin and 4-methylresorcin.

As the aromatic dithiol (d1), benzene-1,4-dithiol, benzene-1,3-dithiol, 2,6-naphthalene-dithiol, 2,7-naphthalene-dithiol And the like.

As the aromatic thiophenol (d2), 4-mercaptophenol, 3-mercaptophenol, 6-mercaptophenol and the like can be mentioned.

Examples of the aromatic thiolcarboxylic acid (d3) include 4-mercaptobenzoic acid, 3-mercaptobenzoic acid, 6-mercapto-2-naphthoic acid, and 7-mercapto-2-naphthoic acid.

As the aromatic hydroxyamine and aromatic diamine compounds (e), 4-aminophenol, N
-Methyl-4-aminophenol, 1,4-phenylenediamine, N-methyl-1,4-phenylenediamine,
N, N'-dimethyl-1,4-phenylenediamine, 3
-Aminophenol, 3-methyl-4-aminopheno-
2-chloro-4-aminophenol, 4-amino-
1-naphthol, 4-amino-4'-hydroxydiphenyl, 4-amino-4'-hydroxydiphenylether, 4-amino-4'-hydroxydiphenylmethane,
4-amino-4'-hydroxydiphenyl sulfide,
4,4'-diaminophenyl sulfide (thiodianiline), 4,4'-diaminodiphenyl sulfone, 2,5-
Diaminotoluene, 4,4'-ethylenedianiline,
4,4'-diaminodiphenoxyethane, 4,4'-diaminodiphenylmethane (methylenedianiline),
4'-diaminodiphenyl ether (oxydianiline) and the like.

The thermotropic liquid crystal polyester which can be used in the present invention can be produced from the above monomers by various ester forming methods such as a melt acidification method and a slurry polymerization method.

In terms of molecular weight, that of the thermotropic liquid crystal polyester suitable for use in the present invention is about 200
0-200000, preferably about 4000-10000
0. The molecular weight can be measured, for example, by measuring the terminal groups of the compressed film by infrared spectroscopy. G, which is a general measurement method involving solution formation,
It is also possible to use a PC.

Among the thermotropic liquid crystal polymers obtained from these monomers, an aromatic polyester which is a (co) polymer containing a monomer unit represented by the following general formula (1) as an essential component is preferable. The monomer unit preferably contains about 50 mol% or more.

[0035]

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A particularly preferred aromatic polyester which can be used in the present invention is a polyester represented by the following formula (2) having a repeating unit having a structure derived respectively from three compounds of p-hydroxybenzoic acid, phthalic acid and biphenol. It is. The repeating unit having a structure derived from biphenol of the polyester represented by the following formula (2) may be a polyester in which part or all of the repeating unit is substituted with a repeating unit derived from dihydroxybenzene. A polyester represented by the following formula (3) having a repeating unit having a structure derived from two kinds of compounds, p-hydroxybenzoic acid and hydroxynaphthalenecarboxylic acid.

[0037]

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[0038]

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The thermotropic liquid crystal polymer that can be used in the present invention may be used alone, but two or more of them can be used as a mixture.

The thermotropic liquid crystal polymer may be used by blending a non-liquid crystal resin. The resin that can be blended may be either a thermoplastic resin or a thermosetting resin, but is preferably a polyamide resin, a polycarbonate resin, a polyethylene terephthalate resin, a polybutylene terephthalate resin, a polyphenylene sulfide resin, a polyether sulfone resin, or a polysulfone resin. So-called thermoplastic engineering plastics (non-liquid crystalline) such as polyetherketone resin and polyetheretherketone resin are exemplified. The blending amount of the thermoplastic resin is 1 to 200 parts by weight, preferably 1 to 100 parts by weight, more preferably 1 to 100 parts by weight per 100 parts by weight of the thermotropic liquid crystal polymer in the present invention.
５０50 parts by weight.

Incidentally, a reinforcing agent or a filler can be added to the thermotropic liquid crystal polymer usable in the present invention in order to further improve heat resistance and mechanical properties. Specific examples of reinforcing agents or fillers include fibrous, powdery and mixtures of both. Examples of the fibrous reinforcing agent include glass fiber, shirasu glass fiber, alumina fiber, silicon carbide fiber, ceramic fiber, asbestos fiber, gypsum fiber, and metal fiber (for example, stainless steel fiber).
And carbon fibers (including graphite fibers). Further, as a powdery and granular reinforcing agent, silicates such as walasteinite, sericite, kaolin, mica, clay, bentonite, asbestos, talc, alumina silicate, alumina, silicon oxide, magnesium oxide,
Metal oxides such as zirconia and titanium oxide; carbonates such as calcium carbonate, magnesium carbonate and dolomite; sulfates such as calcium sulfate, calcium pyrophosphate and barium sulfate; glass beads; boron nitride; silicon carbide; These may be hollow (for example, hollow glass fiber, glass micro balloon, shirasu balloon, carbon balloon, etc.). If necessary, the above-mentioned reinforcing agent may be pretreated with a silane-based or titanium-based coupling agent before use.

The thermoplastic resin usable in the present invention, for example, a thermotropic liquid crystal polymer, includes an antioxidant and a heat stabilizer (for example, hindered phenol, hydroquinone, phosphite) as long as the object of the present invention is not impaired. , And their substitutes), UV absorbers (eg, resorcinol, salicylate, benzotriazole, benzophenone, etc.), lubricants and release agents, dyes (eg, nitrosine, etc.), and pigments (eg, cadmium sulfide, phthalocyanine, carbon) Ordinary additives such as a coloring agent containing a black (eg, black), a flame retardant, a plasticizer, and an antistatic agent can be added to impart predetermined characteristics. The reinforcing agent, the filler and the like can be blended in an amount of 80% by weight or less, preferably 70% by weight or less based on the whole resin composition.

In injection molding of the thermotropic liquid crystal polymer, the injection molding conditions include a resin temperature of 200 to 42.
0 ° C., mold temperature 60 to 170 ° C., more preferably 60 to 170 ° C.
It can be appropriately selected from a range of 130 ° C., an injection pressure of 50 to 4000 kg / cm ² , and an injection speed of 5 to 1000 mm / sec.

When the actuator of the present invention has three or more arms, usually the outermost two arms are used.
The thickness of each arm is made smaller than the thickness of the inner arm. Usually, the outermost two blades have the same thickness, but they can be different. When there are two or more inner arms, their thicknesses may be the same or different. In the relationship between the thicknesses of the outer and inner arms, more preferably, the ratio of T1 / T2 is 1.05 to 2.0, where T1 is the thickness of the inner arm and T2 is the thickness of the outer arm.
0, more preferably in the range of 1.1 to 2.0. For the actuator, the thickness itself of each of the outer and inner arm portions is appropriately selected from the range of 0.1 to 10 mm. Also, the length of the arm itself,
It is usually in the range of 1 to 50 cm.

At the time of injection molding, the molten resin flow injected from the primary gate passes through the connecting portion and the gate, and then fills each arm. Finally, the molten resin flows at a position opposite to the rotation axis of the integrated arm. Join. As a result, the thicker arm is filled earlier, and as a result, the resin flow in that portion reaches the junction faster.

Contrary to this configuration, when the outermost arm is thick, the resin flow from the outer arm reaches the junction quickly, so that gas entrainment occurs at the junction. It will be easier. This is undesirable because it leads to a decrease in mechanical strength. The gas is generated from a molten resin or a filler, but a resin that melts at a higher temperature, such as an engineering plastic such as a thermotropic liquid crystal polymer, tends to generate a gas. In particular, care must be taken to avoid gas entrapment. Therefore, a configuration in which the thickness of each of the two outermost arms is smaller than the thickness of each of the inner arms is particularly advantageous when a thermotropic liquid crystal polymer is used.

[0047]

FIG. 1 is a side view showing an arm intermediate product according to an embodiment of the present invention, and FIG. 2 is a plan view of a connecting portion thereof. As shown in these figures, this intermediate product connects a plurality of arms 1 with a sprue 6 and an integral arm portion 2 integrally including a plurality of arms 1 used for an actuator of a disk drive. The connecting part 3 to be removed, the primary gate 5 existing between the sprue 6 and the connecting part 3, and the three two gates existing between the connecting part 3 and the plurality of arms 1 of the integral arm part 2. And a next gate 4.

Each secondary gate 4 is connected to the tip of each arm 1. The connecting portion 3 has a columnar shape extending in a direction perpendicular to each arm 1 and having a length at least equal to or greater than the distance between the arms 1 at both ends, and has a thickness similar to the thickness of each arm 1. It has a cylindrical shape. The primary gate 5 connects a sprue 6 extending in parallel with the connecting portion 3 in the axial direction thereof to the connecting portion 3, and a film gate extending substantially the length of the connecting portion 3 in the axial direction. It is.
The thickness d of each secondary gate 4 at a portion adjacent to the arm 1 has a relationship of 0.9D <d with the thickness D of the arm 1 to which it is connected.

The integral arm portion 2 has a carriage 7, and when used as an actuator, a rotary shaft is inserted into this portion and held rotatably.

When this arm intermediate product is injection molded,
The molten resin is injected into the connecting portion 3 through the sprue 6 and the primary gate 5. The injected resin flows into each arm 1 from the connection part 3 via the secondary gate 4. At this time, the resin flows from the secondary gates 4 substantially simultaneously. The resin that has flowed into each arm 1 meets on the carriage 7 to generate a weld.

In the conventional process, when the filling of the resin into all the cavities is completed in this way, the volume shrinkage proceeds in all the cavities, so that it is necessary to maintain the pressure to further replenish the shrinkage. In order to perform the replenishment by the holding pressure without any trouble, it is preferable that the dimensions and the like of the secondary gate and the primary gate are set so that the solidification of the secondary gate precedes the solidification of the primary gate. If the solidification of the primary gate precedes the solidification of the secondary gate, it is impossible to compensate for the volume contraction progressing in the integrated arm portion 2 after the solidification of the primary gate by holding pressure. Therefore, the progress of the filling / solidification includes the completion of the filling of all cavities, the progress of volume contraction in all the cavities, the completion of the pressure filling in the integral arm part 2, the solidification of the secondary gate 4, the completion of the pressure holding in the connecting portion 3, and the primary. It is preferable to design so that the gate 5 is solidified. After the solidification of the primary gate 5 is completed, the mold is released, and an intermediate product having the sprue 6, the primary gate 5, the connecting portion 3, the secondary gate 4, and the integrated arm portion 2 is taken out.

The thus obtained intermediate product of the integral arm can be made into an integral arm (corresponding to the integral arm portion 2) by further solidifying and then separating the connecting portion 3.

Conventionally, it can be said that the arm intermediate product removed from the mold is insufficiently solidified from the viewpoint of obtaining long-term dimensional stability. However, as shown in FIG.
By causing the solidification process to proceed while the arm 1 is connected to each arm 1, deformation and warping of each arm 1 during that time are suppressed, and the parallelism between the arms 1 is maintained. Therefore,
After the solidification step, the integral arm obtained by separating the unnecessary connecting portion 3 has high dimensional accuracy and the yield is improved. Further, since the integrated arm including each arm 1 and the carriage 7 is formed simultaneously and integrally, the manufacturing process is shortened.

The integrated arm intermediate product itself taken out of the mold or the integrated arm portion having the connecting portion 3 except for the sprue 6 or the sprue 6 and the primary gate 5 from the intermediate product is annealed. Is also good.
In this case, an integrated arm can be obtained by cutting between the secondary gate 4 and the arm 1 after annealing.

In the case where a sprue or a runner is used as the connecting portion as in the prior art, the resin from the portion adjacent to the injection nozzle to the inside of the connecting portion does not remain when the screw of the injection device is retracted at the end of the injection molding. Because of the solidification state, the pressure of the connecting portion suddenly becomes zero from the holding pressure for supplying the resin that compensates for the solidification shrinkage of the resin in the cavity. At this time, if the resin in the unsolidified state undergoes elastic recovery and changes its dimensions, and its elastic recovery force exceeds the elastic modulus of the solidified outer layer and deforms the outer layer, then the atmospheric pressure is further increased. When the unsolidified resin is cooled and solidified below, the volume also contracts. Therefore, the dimensions of the connecting portion are not stable. Further, when the pressure applied to the screw is switched from the high compression pressure after completion of filling of the resin to the low holding pressure, due to a delay in pressure transmission, the magnitude of the force applied to the screw reverses, and the screw retreats. There is also. In that case, the volume from the tip of the screw to the connecting portion changes, and the pressure gradient pattern changes. Therefore, the time-series pressure fluctuation pattern at the connecting portion is poor in reproducibility, which also makes it difficult to stabilize the size of the connecting portion.

On the other hand, according to the present embodiment, the connecting portion 3 is separated from the sprue 6 by the primary gate 5, and the pressure of the connecting portion 3 varies with the pressure fluctuation at the nozzle tip of the injection device. No similar pressure fluctuations. That is, even if the screw of the injection device retreats at the end of the injection molding, the pressure of the connecting portion 3 does not suddenly become zero and the pressure of the arm 1 ends because the primary gate 5 is solidified before that. It exhibits a highly reproducible variation close to the same pressure variation pattern as the part. This means that the connecting portion 3 is solidified in the mold in the same manner as the integral arm 2 portion. Therefore, the dimensional reproducibility and stability of the connecting portion 3 are ensured, the original function of fixing the dimension of the tip of the arm 1 inherent in the connecting portion 3 is favorably exhibited, and the dimensional accuracy of the arm 1 can be improved. That is, specifically, for example, in FIG. 1 which is a side view showing an intermediate body of an arm according to an embodiment of the present invention, the distance between a plurality of arms and the distance between each arm and a reference surface (for example, the surface of the carriage 7) are shown. The distance stabilizes and becomes a value as designed. On the other hand, when the spray or the runner is used as the connection part (in the case of one gate), the stability of these distances is reduced.

Further, by setting the thickness of the connecting portion 3 to be substantially the same as the thickness of each arm 1, the solidification time of the connecting portion 3 and each arm 1 can be made substantially the same, so that the efficiency is improved. Molding can be performed.

Further, when a resin is injected from or near the tip of the arm 1 toward the longitudinal direction of the arm 1 for injection molding, the thermoplastic resin, for example, the molecules of a thermotropic liquid crystal polymer are oriented in the flowing direction of the resin. I do.
By this orientation effect, the fibrous filler (preferably having an aspect ratio of 3 or more) oriented in the polymer is also strongly oriented in the flow direction at the same time. Therefore,
Various functions given to the resin mixed with the fibrous filler for a mechanical reinforcing effect and the like are further improved by the orientation. These functions include, in addition to the reinforcing effect, a reduction in surface resistance when a conductive and fibrous filler is used.

More specifically, since plastic is essentially not conductive, molded articles made of plastic, especially electric parts, are often made conductive for measures against static electricity and for other reasons. For this purpose, it is conceivable to mix conductive fillers including fibrous fillers. However, the conductivity of the conductive filler itself cannot be sufficiently exhibited simply by blending and injection molding. As described above, it is necessary to strongly orient the fibrous and conductive filler. By such a strong orientation, the conductivity is significantly improved as compared with a product simply molded by injection molding and without directionality (without orientation). This conductivity is determined, for example, from the surface resistance of an injection-molded article such as an arm.

As the filler for this purpose, metal fibers, metal-coated inorganic fibers, metal whiskers, etc.
Examples include carbon fiber and graphite fiber. Carbon fibers and graphite fibers are preferred because they are usually conductive and can also be expected to have a mechanical reinforcing effect. The compounding amount of these fibrous fillers is selected from the range of the compounding amount of the filler described above.

Here, as the thermoplastic resin, a thermotropic liquid crystal copolyester having a repeating unit each derived from parahydroxybenzoic acid, terephthalic acid, isophthalic acid and biphenol (optical differences due to melting when observed by a polarizing microscope). The melting point by DSC was 360 ° C.) A resin composition comprising 100 parts by weight of 30 parts by weight of carbon fiber (aspect ratio 4) was used.

Since the molecules of the integrated arm thus obtained are oriented as described above, the coefficient of linear expansion of the arm is close to that of metal. That is, since the resin flows from the tip of each arm 1, the molecules of the resin are oriented in the longitudinal direction of the arm 1, and the linear expansion coefficient in this direction is the width direction (perpendicular direction).
Becomes smaller than the coefficient of linear expansion. This tendency is remarkable in the thermotropic liquid crystal polymer. In this liquid crystal polymer, the linear expansion coefficient in the longitudinal direction of the arm 1 is particularly small as a resin, and is close to that of a metal. A small coefficient of linear expansion leads to a high dimensional accuracy, and the dimensional accuracy of the arm of the actuator is important in the longitudinal direction. Therefore, a high dimensional accuracy in the longitudinal direction is particularly advantageous. Therefore, when the actuator is constituted by the integral arm, the dimensional accuracy with respect to the metal part is high and the rigidity is high.

The solidification time of the intermediate product is, for example, in the range of 1 minute to several hours, depending on the resin, and is left for several days in some cases. Since the mold is usually cooled, it is possible to solidify it by leaving it in the mold for a sufficient time. However, this makes the molding time too long and is uneconomical.
Therefore, usually, after being taken out of the mold, it is left to stand and sufficiently solidified, and then the connecting portion 3 is cut and removed to form an integrated arm.

It is to be noted that there is also a method in which each arm is formed independently without forming the connecting portion 3, and after taking out from the mold, each arm 1 is supported and fixed by an appropriate method until it is solidified. To get the mold out of the mold,
Since each arm 1 is easily deformed during operations such as supporting and fixing, it is not preferable. This is because it is most easily deformed when taken out of the mold. In addition, there may be a plurality of connecting portions 3. However, one connecting portion 3 is usually sufficient. Due to the presence of the connecting portion 3, the relative positional displacement of each arm 1 is reduced. For example, there is little deformation due to a protruding pin for releasing the mold. Therefore, the connecting portion 3 can have a length, a width, a thickness, and the like that reduce deformation due to the reinforcing effect. However, as described above, the thickness of the connecting portion 3 is preferably substantially the same as the thickness of each arm 1 in terms of manufacturing.

An actuator can be formed by fixing a movable coil for applying a force for swinging the integrated arm obtained as described above to the arm. For this purpose, the movable coil is set in a mold as an insert when the integral arm intermediate product is injection-molded, and the resin is surrounded around the movable coil so that the intermediate product of the integral arm is placed in the middle of the actuator. Can be manufactured as a product. In that case, the terminal pins for connection of the coil conductor are also inserted as necessary.
Also in this case, by removing the connecting portion after the intermediate product is sufficiently solidified, an actuator with high dimensional accuracy of the arm can be obtained. According to this, the actuator can be manufactured by a method with a small number of necessary members and a small number of steps.

FIG. 3 is a side view showing an intermediate arm product according to another embodiment of the present invention, and FIG. 4 is a plan view of a connecting portion thereof. In this case, the gate 8 connects the sprue 6 extending in parallel with the connecting portion 3 and in parallel with the axial direction thereof to the connecting portion 3 at substantially the same position as each arm 1 as viewed in the axial direction. Therefore, the number of gates 8 is equal to the number of arms 1. Other points are the same as those in FIG.

FIG. 5 is a side view showing an intermediate arm product according to still another embodiment of the present invention. In this case, the gate 9 connects the sprue 6 extending in the axial direction to the connecting portion 3 in series and one end of the connecting portion 3. Other points are the same as those in FIG.

[0068]

As described above, according to the intermediate product of the integrated arm and the injection molding method of the present invention, a connecting portion for connecting a plurality of arms of the integrated arm portion is provided, and the connecting portion and the sprue and / or the runner are connected. A primary gate is provided between the connecting portions and a secondary gate is provided between the connecting portion and the integral arm portion, or the molten resin is connected to the molten resin from a sprue and / or runner via the primary gate. Flow into each arm through the secondary gate, and until the intermediate product of the integrated arm is sufficiently solidified, the connecting portion is provided with good dimensional stability and good multi-arm performance. It can be used as fixing means. Therefore, an integrated arm having a plurality of arms with high dimensional accuracy can be provided.

Since the secondary gate is connected to the tip of each arm, the coefficient of linear expansion in the arm direction can be made closer to that of the metal, and the dimensional accuracy for the metal can be improved. Further, the rigidity in the arm direction can be improved.

Further, since the connecting portion is formed in a column shape extending in a direction perpendicular to each arm and having a length longer than at least the distance between the arms at both ends, substantially simultaneously and uniformly with respect to each arm. Molten resin can flow in.

Further, since the connecting portion is formed in a cylindrical shape having a thickness substantially equal to the thickness of each arm, the solidifying time of the connecting portion is made substantially the same as the solidifying time of each arm, thereby improving the efficiency. Manufacture can be performed, and the stability with respect to the dimension of the connecting portion can be improved.

Further, since the integrated arm intermediate product is taken out of the mold after the inflow resin is solidified, the dimensional change of the connecting portion after taking out can be suppressed, and the dimensional accuracy of the plurality of arms can be further improved.

Also, the intermediate product itself taken out of the mold or the integrated arm having at least the connecting portion except for the sprue and / or runner or the sprue and / or the runner and the primary gate from the intermediate product may be annealed. Therefore, after annealing, the secondary gate and the arm are cut off, so that an integrated arm with higher dimensional accuracy can be provided.

[Brief description of the drawings]

FIG. 1 is a side view showing an arm intermediate product according to an embodiment of the present invention.

FIG. 2 is a plan view of a portion of a connecting portion of the intermediate product of FIG. 1;

FIG. 3 is a side view showing an arm intermediate product according to another embodiment of the present invention.

FIG. 4 is a plan view of a connecting portion of the intermediate product of FIG. 3;

FIG. 5 is a side view showing an arm intermediate product according to still another embodiment of the present invention.

[Explanation of symbols]

1: arm, 2: integral arm, 3: connecting portion, 4: gate-like portion, 5, 8, 9: gate, 6: sprue, 7: carriage.

Claims (12)

[Claims] 1. A part of an integral arm integrally including a sprue and / or runner and a plurality of arms used for an actuator of a disk drive; and at least the plurality of arms are connected and finally removed. One connecting part, a primary gate existing between the sprue and / or runner and the connecting part, and a secondary gate existing between the connecting part and a plurality of arms of the integrated arm part. An intermediate product of an integrated arm. 2. The integrated arm intermediate product according to claim 1, wherein said secondary gate is connected to a tip of each arm. 3. The connecting portion according to claim 1, wherein the connecting portion has a column shape extending in a direction perpendicular to each arm and having a length at least equal to a distance between arms at both ends. One-piece arm intermediate product. 4. The integrated arm intermediate product according to claim 3, wherein said connecting portion is a cylindrical member having a thickness substantially equal to a thickness of each arm. 5. The primary gate is connected to the connecting portion with the sprue and / or runner extending in parallel with the connecting portion in parallel with the axial direction, and the primary gate is substantially connected to the connecting portion in the axial direction. 5. The integral arm intermediate product according to claim 3, wherein the intermediate product is a film gate extending over a length. 6. The primary gate is configured such that the sprue and / or runner extending in parallel with the connecting portion and in parallel with the axial direction thereof and the connecting portion have substantially the same position as each arm when viewed in the axial direction. 5. The integrated arm intermediate product according to claim 3, wherein the same number of gates as the number of said arms are connected. 7. The primary gate is a gate that connects the sprue and / or runner extending in the axial direction in series with the connecting portion and one end of the connecting portion. 5. The intermediate product for an integral arm according to 3 or 4. 8. The integrated arm according to claim 1, wherein the thickness d of the secondary gate has a relationship of 0.9D <d with the thickness D of the arm to which the secondary gate is connected. Intermediate products. 9. An injection molding method for an integral arm having a plurality of arms integrally used for an actuator of a disk drive, wherein a molten resin is supplied from a sprue and / or a runner via a primary gate to the plurality of arms. And then flowing the molten resin from the connection portion to each arm through a secondary gate. 10. After the inflow resin is solidified, the sprue and / or runner, primary gate, connecting portion,
The method of claim 9, wherein the intermediate product including the next gate and the plurality of arms is taken out. 11. The intermediate product itself taken out of the mold, or an integrated arm having at least the connecting portion except for the sprue and / or runner or the sprue and / or runner and the primary gate from the intermediate product. 3. The method according to claim 1, wherein annealing is performed.
0. An injection molding method for an integral arm according to 0. 12. The method according to claim 11, wherein a portion between the secondary gate and the arm is cut after annealing.