JP2008062387A - Mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold which still micronizes the relative moving quantity of an inner mold part and an outer mold part and sets the coaxial degree between the inner and outer peripheral surfaces of a molded product with higher precision. <P>SOLUTION: A cylindrical mold comprises the outer mold part 3 and the inner mold part 4, both of which form a cavity 6 and an adjusting mechanism 5 for adjusting the position in the radial direction of the outer mold part 3 with respect to the inner mold part 4. The adjusting mechanism 5 is equipped with a first pressure member 51 for pressurizing the outer mold part 3 in an x-direction. The first pressure member 51 has a first taper surface A for guiding the outer mold part 3 in the x-direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a molding die, particularly a molding die suitable for molding a small member.

For example, as a molding die for a resin housing incorporated in a hydrodynamic bearing device, an inner mold portion and an outer mold portion that form a cavity are arranged in the radial direction in order to increase the coaxiality between the inner peripheral surface and the outer peripheral surface of the housing. Those which are capable of relative movement are known. The relative movement in the radial direction of the inner mold part and the outer mold part in this molding die is caused by bringing a feeding means capable of minute advancement and retraction into contact with two surfaces of the outer wall of the outer mold part having a rectangular cross section. (For example, refer patent document 1).
JP 2005-88427 A

  By the way, in general, as the member size becomes smaller, the order of various precisions (coaxiality, parallelism, etc.) required for the member to be molded becomes smaller. For example, in recent years, demands for further miniaturization, higher speed rotation, higher rotation accuracy, etc. have been increasing in the above-described hydrodynamic bearing devices. In the configuration in which the amount of movement of the mold part is synchronized, the number of cases where the required coaxiality cannot be satisfied is increasing.

  An object of the present invention is to provide a molding die that can further reduce the relative movement amount of an inner mold part and an outer mold part, and thereby can further improve various precisions required for a molded product. .

  In order to solve the above-described problems, the present invention provides a molding die that includes an inner mold part and an outer mold part that form a cavity, and is capable of relative movement between the inner mold part and the outer mold part. A molding die comprising: a first pressure member that pressurizes one of the mold parts in a first direction; and a first taper surface that guides the first pressure member in the first direction. provide.

  As described above, in the molding die according to the present invention, the first pressurizing member that pressurizes either the inner mold part or the outer mold part in the first direction, and the first pressurizing member is the first pressurizing member. And a first tapered surface that guides in one direction. According to this configuration, it is possible to reduce the amount of movement of any one mold part in the first direction according to the inclination angle of the first tapered surface. That is, for example, when the advance / retreat amount of the first pressure member is 1 and the inclination angle of the first taper surface is α, the advance / retreat amount of the one mold part in the first direction is tan α. If the inclination angle α is set to be less than 45 °, the advance / retreat amount of the mold part can be suppressed to tan α times compared to the conventional configuration. Thereby, compared with the conventional configuration, it is possible to easily increase the accuracy of the molded product to be molded. The first tapered surface can be provided on one or both of the first pressure member and the member that guides the first pressure member.

  The molding die according to the present invention further includes a second pressure member that pressurizes the one mold part in the second direction, and a second pressure member that guides the second pressure member in the second direction. The taper surface can be provided. As a result, the molding die can be moved in a small amount in two directions, and the accuracy of the molded product can be further increased. Of course, the second tapered surface can also be provided on one or both of the second pressure member and the member that guides the same as the first tapered surface.

  The first and second directions can be orthogonal to each other in the radial direction of the molded product. Thereby, positioning of the inner mold part and the outer mold part in the radial direction can be performed with high accuracy, and the coaxiality between the inner surface and the outer surface of the molded product can be increased.

  The inclination angle of the first and second taper surfaces depends on the accuracy required for the molded product, but if it is too large, it is difficult to adjust the relative position of the inner mold portion and the outer mold portion with high accuracy. On the other hand, if it is too small, the advancing / retreating strokes of the first and second pressure members necessary to obtain the movement amount of the mold part become large, the mold becomes large and the structure becomes complicated. For this reason, the inclination angles of the first and second tapered surfaces are preferably set to 1 ° to 10 °, and more preferably set to 2 ° to 5 °. This is to eliminate the disadvantages of increasing and decreasing the inclination angle of the tapered surface described above in a well-balanced manner.

  As described above, the molding die according to the present invention can position the other with high precision with respect to either the inner mold part or the outer mold part forming the cavity, so that a high degree of coaxiality is provided between the inner surface and the outer surface. It can be suitably used as a molding die for molding a required cylindrical body, for example, a housing for a hydrodynamic bearing device.

  As described above, according to the present invention, it is possible to further reduce the relative movement amount of the inner mold portion and the outer mold portion, thereby providing a molding die that can further increase the accuracy required for a molded product. can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1A conceptually shows a molding die according to the present invention, and the molding die shown in FIG. 1 conceptually shows a cylindrical molding die. The molding die includes a fixed mold 1 and a movable mold 2 that is guided by, for example, a guide pin (not shown) and is movable in the axial direction (axial direction of the molded product) with respect to the fixed mold 1.

  The fixed die 1 has a gate 1 a communicating with the cavity 6, an inner peripheral surface 3 a thereof serving as an outer wall surface of the cavity 6, and an outer die portion 3 movable in the radial direction and a radial position of the outer die portion 3 are adjusted. And an adjusting mechanism 5. As the gate 1a, a known gate shape such as a point gate (including a multi-point gate), a ring gate, or a film gate can be adopted, and is appropriately selected according to the size / shape of the molded product and the injection material.

  The movable mold 2 includes an inner mold portion (core pin) 4 whose outer peripheral surface 4 a constitutes the inner wall surface of the cavity 6. In this embodiment, the inner mold part 4 is a fixed mold part.

  As shown in FIG. 1B, the outer mold part 3 and the adjustment mechanism 5 are accommodated in the accommodating part 7 provided in the fixed mold 1. The adjustment mechanism 5 is disposed at a position facing the outer wall surface 3b of the outer mold part 3 having a rectangular cross section at 180 ° in order to position the outer mold part 3 in the first direction (x-axis direction in the drawing). In order to position the first pressurizing member 51 and the support member 52 and the outer mold part 3 in the second direction (y-axis direction in the figure), the outer wall surface 3b of the outer mold part 3 is the same as described above. The second pressurizing member 53 and the support member 54 are arranged at positions facing each other at 180 °. The pressure members 51 and 53 and the support members 52 and 54 are connected to a feeding means 55 capable of precision feeding, such as an adjusting screw, and the pressure members and the support members are moved forward and backward. Position adjustment, that is, positioning of the outer mold portion 3 in the radial direction is performed.

  In the present embodiment, the outer surface of the first pressure member 51 and the inner wall surface of the accommodating portion 7 with which the first pressure member 51 abuts are inclined by an angle α with respect to the y axis so as to move the outer mold portion 3 in the x axis direction. In addition, a first tapered surface A that guides the pressing member 51 in the x-axis direction is provided. Therefore, for example, when the first pressure member 51 is moved downward in the drawing by L, the first pressure member 51 is simultaneously advanced by L × tan α in the −x axis direction. That is, in this case, the feed amount (movement amount of the outer mold part 3) applied to the outer mold part 3 by the first pressure member 51 is L × tanα in the −x-axis direction. Is set to be less than 45 °, the amount of movement of the outer mold part 3 in the x-axis direction is L × (1 compared to the case where the outer mold part 3 is directly moved as in the prior art. -Tan α).

  Similarly, the outer surface of the second pressure member 53 and the inner wall surface of the accommodating portion 7 with which the second pressing member 53 abuts are inclined by an angle α with respect to the x axis in order to move the outer mold portion 3 in the y axis direction. A second tapered surface B that guides the second pressure member 53 in the y-axis direction is provided. Therefore, similarly to the above, the amount of movement of the outer mold part 3 in the y-axis direction can be reduced by L × (1−tan α) compared to the conventional configuration.

  In the molding die having the above configuration, the cylindrical body can be molded, for example, in the following manner. First, in a state where the molding die having the above configuration is set in the injection molding machine, the position of the outer mold portion 3 is adjusted by the adjusting mechanism 5, and the outer wall surface 3 b of the outer mold portion 3 is restrained by the two pairs of adjusting mechanisms 5. . Then, molding is performed in a state where the temperature of the molding die is stable (trial molding). At the time of molding, molten resin P injected from a nozzle of an injection molding machine (not shown) enters the gate 1b through a runner (not shown) and is filled into the cavity 6 from the gate 1b. The molten resin P filled in the cavity 6 is cooled and solidified, the movable mold 2 is moved to open the mold, and the molded product is taken out.

  Next, the coaxiality between the inner peripheral surface and the outer peripheral surface of the molded product taken out is measured. Based on the measurement result, the feeding members 55 connected to the pressure members 51 and 53 and the support members 52 and 54 of the adjustment mechanism 5 are operated to adjust the radial position of the outer mold part 3, and the degree of coaxiality is adjusted. Correct the madness. This adjustment operation may be performed a plurality of times as necessary. After the adjustment work is completed, the main molding is performed. In addition, about the support members 52 and 54, it is also possible to abbreviate | omit position adjustment of the support members 52 and 54 by elastically supporting this in the advancing / retreating direction.

  Note that the molten resin P to be injected may be either an amorphous resin or a crystalline resin as a base resin, and these can be appropriately selected according to the characteristics required for the molded product. As the amorphous resin, polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI) and the like can be used, and as the crystalline resin, a liquid crystal polymer can be used. (LCP), polyether ether ketone (PEEK), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS) and the like can be used. These are merely examples, and the usable base resins are not limited. These base resins may be mixed with one or more of various fillers such as a reinforcing material (in any form such as a fiber or powder), a lubricant, and a conductive material as necessary.

  As described above, the outer mold part 3 is adjusted and moved in the radial direction by the adjusting mechanism 5 in accordance with the deviation of the coaxiality, and the radial position with respect to the inner mold part 4 is adjusted, so that both axes are coaxial. The degree can be made highly accurate. In particular, in the present embodiment, the first and second pressing members 51 and 53 that pressurize the outer mold portion 3 in the biaxial direction are provided with tapered surfaces, respectively. Therefore, as long as the taper angle of the taper surface is set to an appropriate value, the amount of advancement / retraction of the pressurizing member (feed means) and the amount of movement of the outer mold portion are the same as in the conventional case. The amount of movement of the portion 3 can be reduced, whereby the coaxiality between the inner peripheral surface and the outer peripheral surface of the cylindrical body can be further increased.

  It should be noted that, depending on the size of the cylindrical body to be formed and the required coaxiality, etc., if the inclination angle α of the taper surfaces A and B is too large, the first and second additions when the feeding means 55 is advanced and retracted. The amount of movement of the pressure members 51 and 53 becomes large, and it becomes difficult to correct the deviation of the coaxiality with a predetermined accuracy. On the other hand, if the inclination angle α is too small, the forward and backward strokes of the first and second pressure members 51 and 53 required to obtain the amount of movement of the outer mold part 3 become large, and the mold becomes large and its structure. Is complicated. From the above, the inclination angle α of the tapered surfaces A and B is preferably set to 1 ° or more and 10 ° or less, more preferably 2 ° or more and 5 ° or less. This is to eliminate the disadvantages of increasing and decreasing the inclination angle α of the tapered surfaces A and B in a well-balanced manner.

  In the above description, the configuration in which the first tapered surface A and the second tapered surface B are provided on both the pressure members 51 and 53 and the accommodating portion 7 has been described. However, the first tapered surface A and the second tapered surface A are described. As shown in FIG. 2A, the tapered surface B can be provided only in the pressure members 51 and 53, or can be provided only in the accommodating portion 7 as shown in FIG. 2B. In the present embodiment, the inclination angles of the first taper surface A and the second taper surface B are both α, but the inclination angles of the respective taper surfaces can be different from each other.

  In the above description, the configuration in which the outer mold portion 3 is adjusted and moved in the radial direction has been described. However, the outer mold portion 3 may be fixed and the inner mold portion 4 may be adjusted and moved in the radial direction.

  Since the cylindrical body molded as described above has a very small deviation in the coaxiality between the inner peripheral surface and the outer peripheral surface, the above-described molding die is, for example, for a hydrodynamic bearing device having the following configuration. It can be suitably used when molding the housing.

  FIG. 3 shows an example of the hydrodynamic bearing device 10. The hydrodynamic bearing device 10 seals a shaft member 11, a bearing sleeve 12 into which a shaft portion 11 a of the shaft member 11 can be inserted into an inner periphery, a housing 13 that houses the bearing sleeve 12, and an opening on one end side of the housing 13. A lid member 14 and a seal member 15 located on the other end side of the housing 13 are provided. For convenience of explanation, the lid member 14 side will be described below, and the seal member 15 side will be described as an upper side.

  The shaft member 11 is made of, for example, a metal material such as stainless steel, and includes a shaft portion 11a and a flange portion 11b provided at one end of the shaft portion 11a. Or it can also be set as the hybrid structure which comprised the axial part 11a with the metal and the flange part 11b with resin.

  The bearing sleeve 12 is made of a sintered metal porous body, particularly a sintered metal porous body mainly composed of copper, and is formed in a cylindrical shape. The bearing sleeve 12 can be formed of a soft metal such as brass in addition to a sintered metal.

  On the inner peripheral surface 12a of the bearing sleeve 12, two upper and lower regions serving as radial bearing surfaces of the radial bearing portions R1 and R2 are provided apart from each other in the axial direction. For example, a plurality of dynamic pressure grooves arranged in a herringbone shape are formed.

  Further, a region that becomes the thrust bearing surface of the first thrust bearing portion T1 is provided in all or part of the annular region of the lower end surface 12b of the bearing sleeve 12, and although not illustrated in the region, for example, A plurality of dynamic pressure grooves arranged in a spiral shape or a herringbone shape are formed.

  The housing 13 is a resin injection-molded product molded using the above-described molding die, and is formed in a substantially cylindrical shape. The inner peripheral surface 13a of the housing 13 is formed in a smooth cylindrical surface.

  A bottomed substantially cylindrical lid member 14 made of resin or metal material is fixed to the lower end opening of the housing 13. The lid member 14 includes a cylindrical side portion 14a and a bottom portion 14b that seals a lower end opening of the side portion 14a, and these are integrally formed. In the whole or part of the annular region of the upper end surface 14b1 of the bottom portion 14b, a region serving as a thrust bearing surface of the second thrust bearing portion T2 is provided. A plurality of dynamic pressure grooves arranged in a spiral shape or a herringbone shape are formed.

  The outer peripheral surface 14a1 of the lid member 14 is fixed to the lower end portion of the inner peripheral surface 13a of the housing by an appropriate means such as press fitting or adhesion. At this time, the flange portion 11 b of the shaft member 11 is accommodated in a space formed between the lower end surface 12 b of the bearing sleeve 12 and the upper end surface 14 b 1 of the bottom portion 14 b of the lid member 14. The upper end surface 14a2 of the side portion 14a of the lid member 14 is in contact with the lower end surface 12b of the bearing sleeve 12, whereby a later-described thrust bearing gap is managed to a specified width.

  An annular seal member 15 formed of a metal material or a resin material is fixed to the upper end opening of the housing 13 by press-fitting, bonding, or an appropriate means using both. The inner peripheral surface 15a of the seal member 15 has a diameter that increases in a tapered shape as it goes upward. Between the inner peripheral surface 15a and the outer peripheral surface 11a1 of the shaft portion 11a that faces the inner peripheral surface 15a, the inner peripheral surface 15a gradually increases. An annular seal space S in which the radial dimension gradually increases is formed. In the internal space of the hydrodynamic bearing device 10 sealed with the seal member 15, for example, lubricating oil is injected as a lubricating fluid, and the hydrodynamic bearing device 10 is filled with the lubricating oil. In this state, the oil level of the lubricating oil is always maintained within the range of the seal space S. The seal member 15 can be integrally formed with the housing 13 in order to reduce the number of parts and the number of assembly steps.

  In the hydrodynamic bearing device 10 having the above-described configuration, when the shaft member 11 rotates, a region that becomes a radial bearing surface that is spaced apart from the upper and lower portions of the inner peripheral surface 12a of the bearing sleeve 12 is a radial region with the outer peripheral surface 11a1 of the shaft member 11. Opposing through the bearing gap. As the shaft member 11 rotates, dynamic pressure of lubricating oil is generated in each radial bearing gap, and the shaft member 11 is supported in a non-contact manner in the radial direction by the pressure. As a result, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 11 in a non-contact manner so as to be rotatable in the radial direction are formed.

  In addition, when the shaft member 11 rotates, the region serving as the thrust bearing surface formed on the lower end surface 12b of the bearing sleeve 12 faces the upper end surface 11b1 of the flange portion 11b of the shaft member 11 via the thrust bearing gap. At the same time, a region serving as a thrust bearing surface formed on the upper end surface 14b1 of the lid member 14 faces the lower end surface 11b2 of the flange portion 11b of the shaft member 11 via a thrust bearing gap. As the shaft member 11 rotates, dynamic pressure of lubricating oil is generated in both thrust bearing gaps, and the shaft member 11 is supported in a non-contact manner so as to be rotatable in both thrust directions. Thereby, the 1st thrust bearing part T1 and the 2nd thrust bearing part T2 which support the shaft member 11 so that it can rotate freely in both thrust directions are formed.

  The hydrodynamic bearing device 10 having the above configuration is incorporated in, for example, a spindle motor shown in FIG. This spindle motor for information equipment is used for a disk drive device such as an HDD. The spindle motor is used for a fluid bearing device 10, a disk hub 16 attached to a shaft member 11 of the fluid bearing device 10, and a radial gap, for example. And a stator coil 17 and a rotor magnet 18 and a base member 19 which are opposed to each other. The stator coil 17 is attached to the outer periphery of the base member 19, and the rotor magnet 18 is attached to the inner periphery of the disk hub 16. The disk hub 16 holds one or more disks D such as magnetic disks on the outer periphery thereof. A housing 13 of the hydrodynamic bearing device 10 is mounted on the inner periphery of the base member 19. When the stator coil 17 is energized, the rotor magnet 18 is rotated by the electromagnetic force generated between the stator coil 17 and the rotor magnet 18, and the disk hub 16 and the shaft member 11 are rotated integrally therewith.

  As described above, the hydrodynamic bearing device 10 is incorporated into the motor by fixing the housing 13 to the inner periphery of the base member 19 by means such as adhesion or press fitting. At this time, if the coaxiality between the inner peripheral surface and the outer peripheral surface of the housing 13 is incorrect, the accuracy of the inner peripheral surface of the bearing sleeve 12 fixed to the inner periphery of the housing 13 may be deteriorated. This deterioration of the inner peripheral surface accuracy deteriorates the width accuracy of the radial bearing gap, which contributes to the deterioration of the rotation accuracy of the motor (fluid bearing device 10). On the other hand, if the housing 13 is injection-molded using the above-described molding die, the deviation of the coaxiality between the inner peripheral surface and the outer peripheral surface becomes extremely small. This can contribute to requests for higher rotation accuracy.

  The molding die according to the present invention is suitably used not only for housing a hydrodynamic bearing device but also for molding other cylindrical bodies that require high coaxiality between the inner peripheral surface and the outer peripheral surface. Is possible.

  Although not shown in the drawings, the molding die according to the present invention is not only used to form not only the cylindrical body having both ends opened but also the bottomed cylindrical body having one end closed. It is also possible to use it.

  In addition, the configuration of the present invention forms not only a cylindrical body having a circular cross section as described above, but also a cylindrical body having a non-circular cross section (for example, an elliptical shape) and a hollow body having a rectangular cross section. It can be suitably used for a molding die.

  Furthermore, the structure of this invention can be used suitably also for the shaping | molding die which performs not only radial positioning but axial positioning.

(A) A figure is a longitudinal cross-sectional view of the molding die of the resin cylinder which concerns on this invention, (b) The figure is the cross-sectional view which expanded the principal part of the molding die. It is a figure which shows the other structure of the taper surface provided in a shaping die. It is sectional drawing of the hydrodynamic bearing apparatus incorporating the housing shape | molded with the shaping die based on this invention. It is a schematic diagram showing an example of a spindle motor for information equipment incorporating a hydrodynamic bearing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed type | mold 2 Movable type | mold 3 Outer type | mold part 4 Inner type | mold part 5 Adjustment mechanism 6 Cavity 10 Fluid bearing apparatus 11 Shaft member 12 Bearing sleeve 13 Housing 51 1st pressurization member 53 2nd pressurization member 55 Feed means A 1st 1 taper surface B 2nd taper surfaces R1, R2 Radial bearing portion T1, T2 Thrust bearing portion S Seal space α Inclination angle

Claims (4)

A molding die comprising an inner mold part and an outer mold part forming a cavity, wherein the inner mold part and the outer mold part are movable relative to each other,
A first pressure member that pressurizes either the inner mold part or the outer mold part in a first direction; and a first tapered surface that guides the first pressure member in the first direction. Mold to mold.   The second pressurizing member that pressurizes the one mold part in the second direction, and the second tapered surface that guides the second pressurizing member in the second direction. Molding mold.   The molding die according to claim 2, wherein the first direction and the second direction are orthogonal to each other in the radial direction of the molded product.   The molding die according to claim 2, wherein an inclination angle of the first and second taper surfaces is not less than 1 ° and not more than 10 °.

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