JP5543753B2 - Method for forming powder compact of fine gear - Google Patents

Description

  The present invention relates to a powder molded body in which a raw material is press-molded into a shape approximating that of a micro gear in a process of manufacturing a micro gear having an integral shaft portion from a plastic raw material obtained by adding a binder to a metal powder by a powder metallurgy method. The present invention relates to a molding method.

  In recent years, in the field of production of digital home appliances, advanced medical equipment, IT equipment, etc., with the downsizing and high functionality of devices, the demand for downsizing and thinning of components has been increasing. However, there is a demand for further miniaturization and thinning even in the case of small and thin so-called micro parts. In order to manufacture this kind of microparts, in addition to machining and electrical discharge machining, which are conventional general part manufacturing methods, the use of semiconductor device manufacturing processes and the like has been studied. It is highly effective in that it can be manufactured with high accuracy and in large quantities.

  The powder metallurgy method is a method in which a raw material powder is pressure-molded into a shape approximate to a product to form a powder compact, and then the powder compact is sintered to obtain a product having a desired shape. Here, as a method for forming a powder compact, a raw material powder is filled in a cavity formed in a press die, and the raw material powder is compressed in a uniaxial direction by a punch, and a raw material powder is used. It is roughly classified into an injection molding method in which a plastic raw material kneaded with a large amount of binder (resin and wax, etc.) is injected into a cavity in a mold and filled. The powder compact obtained by the injection molding method is transferred to the sintering process almost as it is, but the powder compact obtained by the injection molding method is subjected to the sintering process after the binder is removed by heating. Moved.

  Although the above-mentioned stamping molding method has the advantage that the powder molded body can be transferred almost directly to the sintering step, the production time is relatively short, but the extremely thin portion (for example, about 0.1 to 0.3 mm) In the case of molding (thickness), it is considered difficult to fill the raw material powder into a narrow space on the side of the pressing die that forms the thin portion. This problem is considered to be solved by reducing the particle size of the raw material powder. However, this measure causes a new problem that the fluidity of the raw material powder is lowered and the filling property is lowered.

  On the other hand, the injection molding method has an advantage that even a shape having an undercut portion, which is difficult to form with a simple stamp structure, can be molded. However, since the material is filled into the cavity only by the applied pressure at the time of injection filling, there is a case where the material is difficult to be filled in a narrow space on the mold side. In addition, since the raw material is injected and filled while being introduced from the outside to the inside of the mold, a pressure loss occurs in the raw material introduction path, which may result in insufficient filling of the raw material. Therefore, improvement in fluidity by increasing the pressure during injection filling and increasing the amount of binder is considered, but the increase in pressure during injection filling is due to separation of the binder and the raw material powder, and only the binder that tends to flow is the mold first. In addition to being unable to fill with good raw material powder because it is filled in a narrow space, the mold clamping pressure must be increased as the injection filling is increased, leading to an increase in the size of the device, and the increase in binder Increases the dimensional shrinkage after sintering and causes deformation problems.

  In view of this, a method has been proposed that can compensate for the drawbacks of the above-described die molding method and injection molding method, and can precisely mold a minute part having a thin portion (Patent Document 1).

JP 2006-344581 A

  The method for molding a powder molded body described in Patent Document 1 is a method in which the plastic raw material in the injection molding method is filled in a pressing mold capable of forming a product shape, and this raw material is pressed with a punch. That is, it is a method combining an injection molding method and an injection molding method, and an extremely thin meat part can be manufactured.

  By the way, the powder molded body formed by pressurizing the plastic raw material has a lower binder than the powder molded body obtained by press molding the raw material powder and is obtained by pressing the raw material powder. It has the following characteristics. For this reason, in the case of a comparatively simple shape such as the cup shape described in Patent Document 1, it can be extracted from the pressing die without damaging the powder compact, but it is a micro having a plurality of teeth. When a gear powder compact is molded, there is a problem that damage such as collapse of the tooth portion is easily caused when the gear is extracted from the pressing die, and it is difficult to obtain a sound powder compact. In order to make it easy to extract the powder compact, there is a method of providing a taper taper, but it is difficult to reliably provide a taper taper for a micro component. Further, in the case of a minute gear, since it is minute, it is difficult to attach the shaft portion with high accuracy. Therefore, it is effective to form a shaft-equipped gear having the shaft portion integrally. However, when forming a gear having an integral shaft portion, it is difficult to produce a punch that can be slidably fitted to a die formed with minute teeth, and a multi-stage punch that can be slidably fitted to the die. There is a need for a molding method that is different from a normal die molding method using the above.

  The present invention has been made in view of the above circumstances, and the main object thereof is to smoothly extract the powder molded body from the mold without damaging the external teeth of the gear portion, and the shaft portion is integrally provided. Another object of the present invention is to provide a method for forming a powder molded body that can form a powder molded body of a micro gear from the above-mentioned plastic raw material into a desired shape with high accuracy by a press molding method.

The fine gear powder molded body forming method of the present invention is a method of forming a fine gear powder molded body in which a shaft portion is integrally provided on a gear portion having external teeth, and the gear portion forming the gear portion. A shaft part die comprising a gear part die having a hole and a shaft part hole forming the shaft part, and a plurality of movable split dies that can be divided by moving radially outward about the shaft part hole. The gear part hole and the shaft part hole are combined by laminating and combining the gear part die and the shaft part die formed by combining the plurality of movable split dies in a shaft direction. To form a cavity according to the shape of the micro gear, and then, to the cavity, a plastic powder and a binder made of a thermoplastic resin and a wax are added in a ratio of 40 to 60% by volume, and the plasticity is kneaded. raw materials was filled with the following Then, the raw material filled in the cavity is pressurized with a punch to form a powder compact of the micro gear in which the shaft portion is integrally provided on the gear portion, and then the shaft portion die is formed into the plurality of the shaft dies. The movable dividing dies are separated, the movable dividing dies are separated from the shaft portion of the powder molded body, and then the gear portion of the powder molded body is brought into contact with the end face of the gear portion. In this manner, the gear unit die is extracted in the axial direction from the gear unit hole of the gear unit die.

  The micro gear according to the present invention is such that a shaft portion is integrally provided at the shaft center of a gear portion having external teeth, and each tooth portion of the external teeth is extremely thin and between the tooth portions. The interval is also very narrow. The molding method of the present invention is a method of molding a powder molded body by pressing a plastic raw material by a press molding method, and has high deformability of the raw material, so that the raw material can enter a fine gap. Such a fine gear powder molded body can be molded into a desired shape with high accuracy in a pressing die.

  In the present invention, when the molded powder molded body is extracted from the pressing die, first, the shaft portion die forming the shaft portion of the minute gear is divided into a plurality of movable split dies, and the formed shaft portion is Separate. As a result, only the gear portion can be brought into contact with the die (gear portion die), and therefore a punch that can be slidably fitted to the die (gear portion die) can be eliminated. Thereafter, the powder molded body can be extracted by extracting the gear portion from the gear portion hole of the gear portion die. In this case, the gear portion is axially moved by the extraction member abutted against the end surface of the gear portion. Extract. That is, since the gear portion is extracted from the gear portion hole while directly supporting the gear portion by the extraction member, the powder compact can be smoothly extracted from the pressing die without damaging the external teeth.

  The micro gear according to the present invention has a shape in which the shaft portion is provided on both end faces of the gear portion, and accordingly, the shaft die of the push die sandwiches the gear portion die. It is arranged on both sides of the part die.

  Further, the micro gear according to the present invention has a shape in which the shaft portion is provided only on one end surface of the gear portion, and according to this, the shaft portion die of the pressing die is one side of the gear portion die. It is characterized by being arranged.

  Further, the shaft portion of the micro gear according to the present invention is a stepped shaft portion having a different diameter, and accordingly, the shaft portion dies have a plurality of shaft dies corresponding to different diameters, The shaft part dies are arranged so as to be laminated in the axial direction.

  Moreover, in the micro gear according to the present invention, the outer diameter of the gear portion is 0.3 to 1 mm, and the module (pitch circle diameter / number of external teeth) of the gear portion is 0.01 to 0.1. It is characterized by that.

  ADVANTAGE OF THE INVENTION According to this invention, the powder molded object of the micro gear with which the axial part was provided integrally can be shape | molded with high precision from a plastic raw material to a desired shape by the press molding method. Moreover, when extracting a powder compact from a pressing die, it can extract smoothly, without damaging the external tooth of a gear part. As a result, it is possible to suitably form a sound micro-gear powder compact.

It is the (a) side view and (b) top view which show the micro gear with an axis | shaft obtained from the powder compact | molding | casting shape | molded by one Embodiment of this invention. It is sectional drawing which shows the process from the mold clamping to the pressure molding of a raw material of the shaping | molding method of one Embodiment. It is sectional drawing which shows the process from mold opening of the shaping | molding method of one Embodiment to taking out of a powder compact. It is a disassembled perspective view which shows the lower mold | type of the metal mold | die used with the shaping | molding method of one Embodiment. It is a top view which shows the eject pin and lower punch of a lower mold | type. It is a side view which shows the other shape example of a micro gear, Comprising: (a) The micro gear which has a stepped shaft part, (b) The micro gear which has a shaft part only in the one side of a gear. It is sectional drawing which shows the formation process of the micro gearwheel which has a stepped axial part. It is sectional drawing which shows the formation process of the micro gear of a one-side shaft part, Comprising: The case where a shaft part is shape | molded below is shown. It is sectional drawing which shows the formation process of the micro gear of a one side axial part, Comprising: The case where an axial part is shape | molded upward is shown.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(1) Microgear FIG. 1 shows the shape of a microgear (hereinafter referred to as a gear) obtained by sintering a powder compact formed by the molding method of one embodiment. The gear 1 includes a gear portion 13 having external teeth 15 formed of a plurality of tooth portions 14 formed on the outer peripheral surface, and concentric with and integrally with the shaft center of the gear portion 13 on both end faces of the gear portion 13. It has the two cylindrical shaft parts 11 and 12 formed. The lengths and outer diameters of the shaft portions 11 and 12 are the same, and hereinafter, one (the upper side in FIG. 1A) is the first shaft portion 11, and the other is the second shaft portion 12. Both the first shaft portion 11 and the second shaft portion 12 have mountain-shaped convex portions 11a and 12a at their tips.

  For example, the outer diameter of the gear portion 13 is 0.3 to 1 mm, the outer diameters of the shaft portions 11 and 12 are 0.1 to 0.9 mm, and the gear portion 13 module (pitch circle diameter / tooth portion). 14) is from 0.01 to 0.1.

(2) Mold Configuration FIGS. 2A to 2C and FIGS. 3A to 3C show a process of molding a powder compact of the gear 1 using a mold according to an embodiment. . The mold is divided into an upper mold 5 and a lower mold (push mold) 6.

(2-1) Upper Die As shown in FIG. 2, the upper die 5 includes an upper ram 51 and a cylindrical upper punch 52 disposed on the lower surface of the upper ram 51 and extending vertically downward. The upper punch 52 is fixed to the lower surface of the upper ram 51 by an upper punch presser 53. The upper punch 52 has an outer diameter corresponding to the outer diameter of the first shaft portion 11 of the gear 1. A concave portion 52 a for forming the convex portion 11 a of the first shaft portion 11 of the gear 1 is formed on the lower end surface of the upper punch 52.

(2-2) Lower Die As shown in FIG. 2, the lower die 6 includes a gear shaft die 63 sandwiched between a first shaft die 61 and a second shaft die 62, and a second shaft die 62. A lower die 64 is disposed below the lower die 64, and an eject pin 65 and a lower punch 66 are provided on the lower die 64. The dice 61 to 64 are stacked in a horizontal state. In the lower die 6, the gear portion 13 of the gear 1 is formed in the gear portion die 63, the first shaft portion 11 of the gear 1 is formed in the first shaft portion die 61, and in the second shaft portion die 62. A second shaft portion 12 of the gear 1 is formed.

  FIG. 4 shows a state where the lower mold 6 is divided. As shown in the figure, the gear part die 63 is formed with a gear part hole 631 penetrating in the vertical direction. The cross-sectional shape and dimensions of the gear portion hole 631 correspond to the outer shape of the outer teeth 15 of the gear portion 13, that is, the inner teeth 635 corresponding to the outer teeth 15 are formed on the inner peripheral surface of the gear portion hole 631. ing. The gear part die 63 has a thickness corresponding to the gear part 13 of the gear 1, that is, the gear part hole 631 has a depth corresponding to the height of the gear part 13. The gear part die 63 is fixed to a die plate (not shown) or the like, and the gear part hole 631 is disposed concentrically with the upper punch 52 of the upper die 5.

  The first shaft die 61 is constituted by a pair of left and right first movable division dies 612 that are divided into two in the left-right direction. Each of the first movable split dies 612 is brought into a united state by contacting the mating surfaces 613 facing each other at the time of molding the powder molded body. A notch 614 having a semicircular arc section is formed to form a first shaft hole 611 having an inner diameter corresponding to the outer diameter of the shaft 11 (see FIG. 2).

  The left and right first movable split dies 612 are installed so as to be movable in the left-right direction, and the two notches 614 are formed in a state where the mating surfaces 613 are brought into contact with each other to form the first shaft die 61. One first shaft hole 611 that is concentrically aligned and penetrates in the vertical direction is formed. The upper punch 52 of the upper mold 5 is slidably inserted into the first shaft hole 611. The left and right first movable split dies 612 can be split by moving from the combined state in the left-right direction (radially outward) around the first shaft hole 611. The thickness of the left and right first movable split dies 612, that is, the depth of each notch 614 (the length of the first shaft hole 611) is set to be somewhat longer than the length of the first shaft 11 of the gear 1. ing.

  The second shaft die 62 has the same configuration as the first shaft die 61, and a pair of left and right second movable split dies in which a notch 624 having a semicircular cross section is formed on the mating surface 623. 622. When the mating surfaces 623 of the left and right second movable split dies 622 are brought into contact with each other and merged, the notches 624 thereof are concentrically aligned to form one second shaft hole 621 penetrating in the vertical direction ( (See FIG. 2). The inner diameter of the second shaft hole 621 corresponds to the outer diameter of the second shaft 12 of the gear 1. The left and right second movable split dies 622 move from the combined state in the left-right direction (radially outward) about the second shaft hole 621, respectively, and can be split. The thickness of the left and right second movable dice 622, that is, the depth of each notch 624 (the length of the second shaft hole 621) is set to be equal to the length of the second shaft 12 of the gear 1. Yes.

  The lower die 64 is formed with an eject pin guide hole 641 having a cylindrical inner peripheral surface penetrating in the vertical direction. The lower die 64 is fixed to the die plate or the like, and the eject pin guide hole 641 is disposed concentrically with the gear portion hole 631 of the gear portion die 63.

  A hollow eject pin 65 is slidably inserted into the eject pin guide hole 641. As shown in FIG. 5, the eject pin 65 is formed such that the outer edge of the cross section is approximately similar to the outer edge of the outer tooth 15 of the gear portion 13, and the dimension is slightly smaller than the outer tooth 15. ing. The eject pin 65 is set so that the tooth portion 651 corresponding to the tooth portion 14 of the external tooth 15 is in phase with the internal tooth 635 of the gear portion hole 631, and the tooth tip of the tooth portion 651 is the eject pin guide hole 641. It slides on the inner peripheral surface and is inserted into the eject pin guide hole 641. The eject pin guide hole 641 only needs to be a hole that can guide the eject pin 65 straight along the vertical direction. In addition to a simple cylindrical shape as shown in the figure, for example, a gear whose cross-sectional shape corresponds to the eject pin 65 is used. It may be a shape.

  A cylindrical lower punch insertion hole 652 is formed in the shaft center of the eject pin 65, and a cylindrical lower punch 66 is slidably inserted into the lower punch insertion hole 652. A concave portion 66a for forming the convex portion 12a of the second shaft portion 12 of the gear 1 is formed on the upper end surface of the lower punch 66 (see FIG. 2A).

  Although not shown, the lower mold 6 has a heating means for heating the plastic raw material filled therein to improve fluidity, and powder molding in which the raw material is pressed and molded. A cooling means for cooling the body is provided.

(3) Molding Next, a procedure for molding a powder compact of the gear 1 using the above mold will be described.
(3-1) Cavity Formation by Clamping First, the lower mold 6 is clamped as shown in FIG. That is, the left and right first movable split dies 612 are combined to form the first shaft portion die 61, and the left and right second movable split dies 622 are combined to form the second shaft portion die 62. The shaft holes 611 and 621 of the shaft dies 61 and 62 are arranged concentrically with the gear hole 631 of the gear dies 63 and the eject pin guide holes 641 of the lower die 64, and with the gear holes 631. The shaft holes 611 and 621 communicate with each other.

  Further, the eject pin 65 is inserted into the eject pin guide hole 641 of the lower die 64 until the upper end surface comes into contact with the lower surface of the second shaft die 62, and the lower punch 66 is inserted into the eject pin 65 with the upper end surface positioned inside the eject pin 65. Insert until it contacts the lower surface of the second shaft die 62. By this clamping, a cavity 10 is formed in the lower mold 6, which is a space where the gear part hole 631 and the shaft part holes 611 and 621 communicate with each other and the lower part is closed by the lower punch 66. The cavity 10 is formed in a shape corresponding to the outer shape of the gear 1.

(3-2) Feeding raw material The lower mold 6 is kept warm at an appropriate warming temperature by the heating means in advance. Then, as shown in FIG. 2B, an appropriate amount of raw material P is introduced into the cavity 10 from the upper opening of the first shaft hole 611 of the first shaft die 61. As the raw material P, a material having plasticity obtained by adding and kneading a binder made of a thermoplastic resin and a wax in a ratio of, for example, 40 to 60% by volume to a metal powder such as iron powder is used. The form of the raw material P is not specifically limited, A powder form or a pellet form is used. The heat retention temperature of the lower mold 6 is set to a temperature higher than the softening point of the wax added to the binder and lower than the softening point of the thermoplastic resin added to the binder. The thermoplastic resin having a softening point of about 160 to 170 ° C. is used, and the wax having a softening point of about 60 ° C. is used. In this case, the heat retention temperature is about 120 ° C.

(3-3) Pressure Molding Next, the process proceeds to pressure molding of the raw material P. For this purpose, the lower mold 6 is heated by the heating means to heat the raw material in the cavity 10 to the molding temperature. The molding temperature is equal to or higher than the softening point of the thermoplastic resin of the raw material P. Then, as shown in FIG. 2C, the upper die 5 is lowered, and the lower end portion of the upper punch 52 is inserted into the first shaft hole 611, whereby the raw material P in the cavity 10 is axially applied with a predetermined load. Pressurize. The raw material P in the cavity 10 is shaped into the shape of the cavity 10, that is, the shape of the gear 1 while being plastically deformed by being compressed by the descending upper punch 52, and is a powder molding with a predetermined density having a shape similar to the gear 1. It is formed into a body 1A.

(3-4) Mold Opening Next, the lower mold 6 is opened, but before that, the heating by the heating means is stopped and the lower mold 6 is cooled by the cooling means, and the powder in the cavity 10 The temperature of the molded body 1A is lowered to about the above heat retention temperature. Therefore, in the powder molded body 1A, although the wax of the binder is softened, the plastic resin is in a cured state.

  Subsequently, the upper die 5 is raised, the upper punch 52 is extracted from the first shaft hole 611, and the upper die 5 is retracted upward. Subsequently, as shown in FIG. 3A, the first shaft portion die 61 and the second shaft portion die 62 are opened. That is, the left and right first movable dividing dies 612 and the left and right second movable dividing dies 622 are respectively divided. Each movable dividing die 612, 622 is divided until the gear portion hole 631 is opened and both end faces of the gear portion 13A of the powder compact 1A are exposed. The powder compact 1A is held in a state where the gear portion 13A is constrained by the gear portion die 63, and the lower end portion of the second shaft portion 12A is supported by the lower punch 66.

(3-5) Extraction of Powder Molded Body After the shaft dies 61 and 62 are divided, as shown in FIG. 3B, the eject pin 65 is raised, and the gear portion 13A of the powder molded body 1A is moved to the gear portion die. 63 is extracted upward from the gear part hole 631. When the eject pin 65 is raised, the upper end surface thereof comes into contact with the lower end surface of the gear portion 13A of the powder compact 1A as shown in FIG. When the eject pin 65 further rises from this state, the eject pin 65 pushes up the gear portion 13A of the powder compact 1A, whereby the gear portion 13A is pulled out from the gear portion hole 631 in the axial direction. When the gear portion 13A is extracted from the gear portion hole 631, the powder compact 1A is released from the restraint by the lower die 6 and can be taken out to the outside as shown in FIG. When the gear portion 13A of the powder molded body 1A is extracted from the gear portion hole 631, the outer teeth of the gear portion 13A slide on the inner teeth 635 of the gear portion hole 631, but smoothly by the action of the softened wax. Extracted.

(4) Operational Effect The molding method according to the above-described embodiment is a press molding method in which the plastic raw material P containing a large amount of binder is filled in the cavity 10 in the lower mold 6 and is compressed by pressing with the upper punch 52. Therefore, the deformability of the raw material P is high, and the raw material P can enter the fine gap. Therefore, the powder compact 1A of the gear 1 which is an extremely small part and has a very small thickness of each tooth portion 14 of the external tooth 15 and a space between the tooth portions 14 is formed into a desired shape with high accuracy. It is possible.

  When the molded powder molded body 1A is extracted from the lower mold 6, first, the upper and lower shaft dies 61, 62 are divided into left and right parts and separated from the formed shafts 11A, 12A, thereby generating gears. Only the portion 13 </ b> A is in contact with the gear portion die 63. Therefore, it is possible to eliminate the need for a punch that is slidably fitted to the mold (gear part die 63). Thereafter, the powder molded body 1A can be taken out from the lower mold 6 by extracting the gear section 13A in the axial direction by the eject pin 65 brought into contact with the lower end surface of the gear section 13A of the powder molded body 1A. In this case, as shown in FIG. 5, since the root of the gear portion 13A, in particular, the root of the tooth portion is extracted while being directly supported by the eject pin 65, it can be smoothly extracted without damaging the external teeth of the gear portion 13A. . As a result, there is an effect that a sound powder molded body 1A of the gear 1 can be suitably molded.

(5) Other shapes of gear The shape of the gear 1 is an example obtained by the molding method according to the present invention, and in addition to this, the gear of the shape shown in FIG. .

(5-1) Gear having stepped shaft portion The shaft portions 11 and 12 of the gear 1 have a uniform diameter, but a gear compact having a stepped shaft portion having a different shaft diameter is formed. The case where it does is demonstrated. In the gear 2 in FIG. 6A, the first shaft portion 11 is a stepped shaft portion that is thick on the gear portion 13 side and thin on the tip side. That is, the first shaft portion 11 has a large diameter shaft portion 117 and a small diameter shaft portion 118.

  The first shaft part die 61 of the lower mold 6 for molding the powder molded body of the gear 2 is divided into upper and lower parts as shown in FIG. 7, and a large diameter side die 67 corresponding to the large diameter shaft part 117 and And a small-diameter die 68 corresponding to the small-diameter shaft portion 118. Each of these dies 67 and 68 is composed of movable split dies 672 and 682 that are divided into left and right, similarly to the first shaft die 61, and in the state in which these movable split dies 672 and 682 are combined, A large-diameter shaft hole 671 that forms the portion 117 and a small-diameter shaft hole 681 that forms the small-diameter shaft portion 118 are formed. Cutouts 674 and 684 having a semicircular cross section that form a large-diameter shaft hole 671 and a small-diameter shaft hole 681 are formed on the mating surfaces of the movable dice 672 and 682, respectively. On the other hand, the upper punch 54 of the upper die 5 has a small diameter at the tip so as to be slidably inserted into the small diameter shaft hole 681.

  In order to mold the powder molded body of the gear 2, as shown in FIG. 7A, the large-diameter side die 67 and the small-diameter side die 68 are combined together with the second shaft portion die 62, and the lower die 6 is assembled. A cavity 20 having a shape corresponding to the gear 2 is formed. Next, the raw material is charged into the cavity 20 in the same manner as described above, and the upper mold 5 is lowered and the raw material is pressed and compressed by the upper punch 54 as shown in FIG. To do. Thereafter, as shown in FIG. 7 (c), the second shaft die 62, the large-diameter side die 67, and the small-diameter side die 68 are divided and opened, and then the gear portion 13A of the powder molded body 2A is ejected by the eject pin 65. Is extracted from the gear part die 63, and the powder compact 2A is taken out.

(5-2) A gear having a shaft portion on one side of the gear portion The gears 1 and 2 are integrally provided with shaft portions (first shaft portion 11 and second shaft portion 12) on both sides of the gear portion 13. 6B, even if the shaft portion (herein referred to as the second shaft portion 12) has a shape provided only on one end surface of the gear portion 13, the present invention can be applied. It can be applied to form a powder compact. In this case, as shown in FIG. 8A, the lower die 6 has the first shaft part die 61 omitted, and the gear part hole 631 of the gear part die 63 is formed slightly deeper than the height of the gear part 13. Has been. On the other hand, the outer peripheral surface of the upper punch 55 of the upper die 5 is formed in an outer tooth shape having a size and shape corresponding to the outer teeth 15 of the gear portion 13 and is slidably inserted into the gear portion hole 631.

  In order to form a powder compact of the gear 3, as shown in FIG. 8A, the second shaft die 62 is combined to form a cavity 30 having a shape corresponding to the gear 3 in the lower mold 6. Thereafter, as in the above method, the raw material is put into the cavity 30, and the upper die 5 is lowered as shown in FIG. 3A is formed, and after the second shaft die 62 is divided and opened as shown in FIG. 8C, the gear portion 13A of the powder molded body 3A is extracted from the gear portion die 63 by the eject pin 65, The powder compact 3A is taken out.

(5-3) Lower Mold Forming Shaft Part Upward The lower mold 6 in FIG. 8 was configured to form the second shaft part 12 below the gear part 13, but is shown in FIG. As described above, the second shaft portion die 62 is omitted, and the upper die 5 uses the upper punch 52 as it is, so that the second shaft portion 12A is formed on the upper side of the gear portion 13A, and the powder of the gear 3 having the same shape is formed. The molded body 1A can be molded.

  In this case, as shown in FIG. 9A, the first shaft die 61 is combined to form a cavity 30 having a shape corresponding to the gear 3 in the lower mold 6. Next, the raw material is charged into the cavity 30 in the same manner as described above, and the upper mold 5 is lowered and the raw material is pressed and compressed by the upper punch 52 as shown in FIG. 8C, after the first shaft die 61 is divided and the mold is opened, the gear portion 13A of the powder molded body 3A is extracted from the gear portion die 63 by the eject pin 65, and the powder molded body 3A Take out.

  1, 2, 3 ... fine gears, 1A, 2A, 3A ... powder compact, 10, 20, 30 ... cavity, 11 ... first shaft portion, 12 ... second shaft portion, 13 ... gear portion, 15 ... external teeth 5 ... Upper die, 52, 54, 55 ... Upper punch, 6 ... Lower die (push die), 61 ... First shaft portion die, 611 ... First shaft portion hole, 612 ... First movable division die, 62 ... Second shaft die, 621 ... second shaft portion hole, 622 ... second movable split die, 63 ... gear portion die, 631 ... gear portion hole, 65 ... eject pin (extraction member), 66 ... lower punch, 672 ... Movable split die, 682 ... Movable split die, P ... plastic raw material.

Claims (5)

A method of molding a powder compact of a micro gear in which a shaft portion is provided integrally with a gear portion having external teeth,
A gear part die having a gear part hole forming the gear part;
A shaft die formed of a plurality of movable split dies formed by forming a shaft hole that forms the shaft portion and moving radially outwardly about the shaft hole,
Using a stamping die with
By combining the gear part die and the shaft part die in which the plurality of movable split dies are combined in the axial direction, the gear part hole and the shaft part hole are communicated with each other, and Form a cavity according to the shape,
Next, the cavity is filled with a raw material having plasticity in which a binder made of a thermoplastic resin and a wax is added to the metal powder at a ratio of 40 to 60% by volume and kneaded ,
Next, the raw material filled in the cavity is pressurized with a punch to form a powder compact of the micro gear in which the shaft portion is provided integrally with the gear portion,
Next, the shaft die is divided into the plurality of movable division dies, and these movable division dies are separated from the shaft portion of the powder compact,
Subsequently, the gear portion of the powder molded body is extracted in the axial direction from the gear portion hole of the gear portion die by an extraction member brought into contact with the end face of the gear portion. Molding method. The micro gear has the shaft portion provided on both end faces of the gear portion,
In response to this, the shaft part die of the pressing die is disposed on both sides of the gear part die with the gear part die interposed therebetween, Powder molding of the micro gear according to claim 1 Body molding method. The minute gear has the shaft portion provided only on one end surface of the gear portion,
In response to this, the shaft die of the push die is disposed on one side of the gear die, and the method for forming a powder compact of a micro gear according to claim 1. The shaft portion of the micro gear is a stepped shaft portion having a different diameter,
Accordingly, a plurality of the shaft dies are provided corresponding to different diameters, and the plurality of shaft dies are laminated in the axial direction. 4. A method for forming a powder compact of a micro gear according to any one of 3 above.   The outer diameter of the gear portion in the micro gear is 0.3 to 1 mm, and the module (pitch circle diameter / number of external teeth) of the gear portion is 0.01 to 0.1. A method for forming a powder compact of a micro gear according to any one of 1 to 4.

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