JP5861879B2 - Method for forming plastic raw material - Google Patents

Description

  The present invention relates to a method for forming a raw material having plasticity.

  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. As a method of manufacturing such a micropart, a molded material approximated to a target shape is formed by filling a mold with a plastic raw material in which a binder is mixed in powder and compressing with a punch, and the obtained molding A method of sintering the body has been proposed (see Patent Document 1).

JP 2006-344581 A

  According to the molding method of the molded body described in the above-mentioned Patent Document 1, there is an advantage that the raw material is sufficiently filled even in the thin portion, and the shape and dimensional accuracy can be obtained at a high level. However, the raw material used in this molding method is difficult to handle because it has plasticity unlike powder, and an operation for supplying a predetermined amount directly into the mold is required, which is complicated in manufacturing. Met. In addition, the filling of the raw material into the mold every time the molding is performed is the same as the general mold molding in which powder is compression-molded. However, in the case of microparts, one molding is required. Since the amount of the raw material used is extremely small, it is inefficient, and only a small amount of air remains in the mold, so that the raw material is not satisfactorily filled into the mold, which may result in molding failure.

  The present invention has been made in view of the above circumstances, and its main purpose is to be able to fill the mold efficiently with raw materials without leaving air, and to suppress the occurrence of molding defects. An object of the present invention is to provide a method for forming a raw material having plasticity.

In the method for molding a raw material having plasticity according to the present invention, a lower die having a mold hole, a lower end surface of the lower die can be brought into contact with an upper end surface of the lower die, and a punch hole opening in the lower end surface is formed in the lower end portion. An upper die, a lower punch that is slidably fitted into the mold hole of the lower die, an upper punch that is slidably fitted to the punch hole of the upper die, and the punch hole in the upper die A raw material storage part that is formed in communication with the punch hole above, adds a binder made of a thermoplastic resin and wax to the metal powder in an amount of 30 to 60% by volume, and stores a heat-kneaded plastic raw material ; Cavity formed by the lower die, the upper die, and the lower punch through the punch holes through the punch holes through the plastic material that is slidably inserted into the raw material reservoir. And the upper punch is slidably penetrated in the plunger along the sliding direction of the plunger, and reciprocally slides, whereby the raw material reservoir and the punch hole Using a molding die device provided to open and close the gate formed between and close the gate and compress the plastic material in the cavity into a molded body when sliding in the cavity direction, With the upper end surface of the lower die, the lower end surface of the upper die, the lower end surface of the upper punch, and the upper end surface of the lower punch aligned with each other, the upper punch is driven to open the gate, A plunger is driven to inject a plastic material from the gate into the punch hole, and then at least one of the upper punch and the lower punch is driven to form a cavity. The plunger is further driven to fill the cavity with the plastic material through the gate, and after the filling of the plastic material into the cavity is completed, the upper punch is driven. And a step of closing the gate and pressing a plastic raw material to compress the plastic raw material in the cavity into a molded body, and a step of extracting the molded body from the mold hole. And

  According to the present invention, the molded material is obtained by injecting the raw material stored in the raw material storage portion into the cavity with the plunger, compressing the raw material in the cavity with the punch and opening the mold, and repeating this operation to form the molding. The body can be obtained continuously. A small amount of raw material can be easily supplied into the cavity by the operation of the plunger, and the molded product can be efficiently manufactured without the trouble of pulling out the punch.

  Moreover, the filling process of the present invention is such that the upper end surface of the lower die, the lower end surface of the upper die, the lower end surface of the upper punch, and the upper end surface of the lower punch are first aligned in the molding die apparatus. The cavity is not formed in the mold. When the upper punch is driven from this state and the gate is opened, the inside of the punch hole into which the raw material is injected by the plunger is in a negative pressure state. For this reason, the raw material is poured into the punch hole smoothly and promptly. Next, the inside of the cavity formed by driving at least one of the upper punch and the lower punch is also in a negative pressure state. For this reason, when the raw material is filled in the cavity by the plunger, the raw material is filled in the cavity smoothly and quickly, and the efficiency of the filling process is improved. Moreover, since the raw material is filled into the cavity in the negative pressure state, it is possible to prevent air from remaining in the cavity after the raw material is filled, and as a result, the occurrence of molding defects can be suppressed, and the thin-walled portion In addition, the raw material is sufficiently filled, and the accuracy of shape and size can be improved.

  In this invention, the said formation process includes the form which drives the said lower punch with the said upper punch, and compresses the raw material which has the plasticity in the said cavity into a molded object.

  In the present invention, at least one of the upper punch and the lower punch is constituted by a plurality of punches, and the filling step includes a form in which the filling step is started from a state in which end faces of all the punches are aligned.

  According to the present invention, there is provided a method of forming a raw material having plasticity that can efficiently fill a mold with a raw material without causing air to remain, and can suppress the occurrence of molding defects. There is an effect.

It is a perspective view which shows the micro gearwheel obtained from the molded object shape | molded with the shaping | molding method which concerns on 1st Embodiment and 2nd Embodiment of this invention. It is sectional drawing which shows a shaping | molding process from the filling process of the shaping | molding method of 1st Embodiment. It is sectional drawing which shows the extraction process of the shaping | molding method of 1st Embodiment. It is a partial cross section figure of the lower die | dye of the shaping die apparatus used in 1st Embodiment. It is sectional drawing which shows the modification of the filling process in the shaping | molding method of 1st Embodiment. It is sectional drawing which shows a shaping | molding process from the filling process of the shaping | molding method which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the extraction process of the shaping | molding method of 2nd Embodiment. It is a partial cross section figure of the upper die | dye of the shaping die apparatus used in 2nd Embodiment. It is a perspective view which shows the micro gearwheel obtained from the molded object shape | molded with the shaping | molding method which concerns on 3rd Embodiment and 4th Embodiment of this invention. It is sectional drawing which shows a shaping | molding process from the filling process of the shaping | molding method of 3rd Embodiment. It is sectional drawing which shows the extraction process of the shaping | molding method of 3rd Embodiment. It is a partial cross section figure of the upper and lower dies of the forming die device used in a 3rd embodiment. It is sectional drawing which shows a shaping | molding process from the filling process of the shaping | molding method which concerns on 4th Embodiment of this invention. It is sectional drawing which shows the extraction process of the shaping | molding method of 4th Embodiment. It is a partial cross section figure of the upper and lower dies of the molding die device used in a 4th embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[1] First Embodiment FIG. 1 shows a micro gear which is a micro part obtained by sintering a molded body molded by the molding method of the first embodiment. The gear 1 has a shape in which cylindrical shaft portions 5 and 6 having the same length are orthogonally extended on both sides from the center of a spur gear portion 4 in which a tooth row 3 composed of a large number of teeth 2 is formed on the outer peripheral surface. It is what has. Examples of the gear 1 include dimension examples in which the outer diameter D1 of the spur gear portion 4 is several hundred μm to several mm and the diameter D2 of the shaft portions 5 and 6 is several tens to several hundred μm.

(1-1) Configuration of Molding Device to be Used FIGS. 2A to 2E and FIGS. 3A to 3D are for molding the molded body of the gear 1 by the molding method of the first embodiment. The process is shown. First, the structure of the molding die apparatus 101 which suitably implements the molding method of the first embodiment will be described with reference to FIG. In the drawing, reference numeral 10 denotes a pressing die, and the pressing die 10 is composed of an upper die 20 and a lower die 30. These dies 20 and 30 are both provided so as to be movable in the vertical direction, and are arranged so as to be able to be separated from each other in the vertical direction.

  Inside the upper die 20 is formed a raw material reservoir 26 that extends in the vertical direction and opens upward. The raw material storage part 26 has a cylindrical inner peripheral surface, and a lower end part thereof is formed in a conical taper part 26a that tapers downward. An upper punch hole 27 extending downward from the lower end of the tapered portion 26 a and opening in the horizontal lower end surface 20 a of the upper die 20 is formed in the upper die 20. The upper punch hole 27 is concentric with the raw material reservoir 26, and a gate 28 is formed between the upper punch hole 27 and the raw material reservoir 26. The inner diameter of the upper punch hole 27 is set to be equal to the diameter of the shaft portions 5 and 6 of the gear 1.

  A raw material P having plasticity is introduced into and stored in the raw material reservoir 26 from the upper opening. As the raw material P, for example, a material obtained by adding and kneading a binder made of a thermoplastic resin and wax to a metal powder such as iron powder at a ratio of about 30 to 60% by volume is used.

  The plunger 40 is slidably inserted into the raw material reservoir 26 from the upper opening. A cylindrical upper punch 50 having a horizontal lower end surface 50 a is pierced through the shaft center of the plunger 40 so as to be slidable along the vertical direction which is the sliding direction of the plunger 40. When the upper punch 50 is lowered, the lower punch is inserted while sliding into the upper punch hole 27, and at this time, the gate 28 is closed by the upper punch 50. When the upper punch 50 is lifted from the state where the gate 28 is closed, the upper punch 50 comes out of the upper punch hole 27 and the gate 28 is opened as shown in FIG.

  The lower die 30 has a horizontal upper end surface 30a with which the lower end surface 20a of the upper die 20 abuts. The lower die 30 is formed with a cylindrical gear part mold hole 31 that opens up and down. An outer lower punch 32 having a horizontal upper end surface 32a is slidable in the gear part mold hole 31 in the vertical direction. Has been inserted. As shown in FIG. 4A, an inner tooth row 31 a that forms the tooth row 3 of the spur gear portion 4 of the gear 1 is formed on the inner peripheral surface of the gear portion mold hole 31. On the other hand, an outer tooth row 32 b is formed on the outer peripheral surface of the outer lower punch 32 so as to be slidably fitted to the inner tooth row 31 a on the inner peripheral surface of the gear portion mold hole 31. A shaft die hole 33 having an inner diameter equivalent to the diameter of the shaft portions 5 and 6 of the gear 1 is formed at the center of the outer lower punch 32. The shaft die hole 33 has a horizontal upper end surface. An inner lower punch 60 having 60a is slidably inserted. The outer lower punch 32 and the inner lower punch 60 are disposed coaxially with the plunger 40 and the upper punch 50 on the upper die 20 side. In addition, as shown in FIG.4 (b), the internal tooth row | line | column 31a which models the tooth row | line | column 3 of the spur gear part 4 of the gear 1 may be formed only in the upper end part of the gear part type | mold hole 31, and in this case The inner peripheral surface of the gear part mold hole 31 below the inner tooth row 31a is simply cylindrical, and the outer lower punch 32 is a columnar shape that is slidably inserted into the cylindrical inner peripheral surface of the gear part mold hole 31. It is supposed to be.

(1-2) Molding Method Next, a method for molding a molded body of the gear 1 using the molding die apparatus 101 will be described with reference to FIGS. 2 and 3. First, as shown in FIG. 2A, the lower end surface on the upper die 20 side and the upper end surface on the lower die 30 side are aligned at a certain height so that no cavity is formed inside the pressing die 10. That is, the lower end surface 20a of the upper die 20 and the upper end surface 30a of the lower die 30 are brought into contact with each other, and the upper end surface 32a of the outer lower punch 32 is brought into contact with the lower end surface 20a of the upper die 20 so The end surface 50a and the upper end surface 60a of the inner lower punch 60 are brought into contact with each other at the same height as the contact surfaces of the upper and lower dies 20, 30. The gate 28 in the upper die 20 is closed because the upper punch 50 is inserted into the upper punch hole 27. Then, the raw material reservoir 26 in the upper die 20 is substantially filled with the raw material P, and the tip of the plunger 40 is inserted into the raw material reservoir 26.

  Next, as shown in FIG. 2B, the upper punch 50 is driven upward to be removed from the upper punch hole 27 and the gate 28 is opened, so that the raw material reservoir 26 and the upper punch hole 27 are communicated. The upper punch hole 27 constitutes a part of the cavity 11, and then the plunger 40 is driven downward to inject the raw material P in the raw material reservoir 26 into the upper punch hole 27 from the gate 28.

  Next, as shown in FIG. 2C, while the outer lower punch 32 and the inner lower punch 60 are driven downward to form the cavity 11, the plunger 40 is further lowered to feed the raw material P through the gate 28 to the gear. The cavity 11 corresponding to the shape of 1 is filled.

  As shown in FIG. 4 (a), the cavity 11 descends the outer lower punch 32 until the upper end portion of the inner tooth row 31 a of the gear portion mold hole 31 is exposed to a depth corresponding to the thickness of the spur gear portion 4. Then, the inner lower punch 60 is lowered from the outer lower punch 32, and portions corresponding to the spur gear portion 4 and the shaft portion 6 of the gear 1 are formed on the lower die 30 side. Further, a portion corresponding to the shaft portion 5 of the gear 1 is formed on the upper die 20 side. The material P is filled into the cavity 11 by pushing the plunger 40 into the material reservoir 26. The steps up to here are the filling step, and when the filling of the necessary amount of the raw material P into the cavity 11 is completed, the molding step is started.

  In the molding process, first, the upper punch 50 is driven downward as shown in FIG. 2D to close the gate 28, and the upper punch 50 is further pushed into the cavity 11 as shown in FIG. The raw material P is pressed and compressed. Accordingly, the spur gear portion 4 and the shaft portion 6 are formed on the lower die 30 side of the cavity 11, and the shaft portion 5 is formed on the upper die 20 side of the cavity 11 (a part of the upper punch hole 27). The molded body 1A is molded.

  When the molded body 1A is formed in the pressing mold 10 in this way, the process proceeds to an extraction process in which the pressing mold 10 is opened to extract the molded body 1A. In the extracting step, as shown in FIG. 3A, the upper die 20 is raised until the lower end surface 20 a becomes the same height as the lower end surface 50 a of the upper punch 50 to expose the upper shaft portion 5. As shown in FIG. 3B, the entire upper die 20 side is raised. Next, on the lower die 30 side, the lower die 30 is lowered as shown in FIG. 3 (c) to expose the spur gear portion 4, and then the lower die 30 and the outer lower punch as shown in FIG. 3 (d). 32 is lowered and the inner lower punch 60 is raised, and the lower shaft portion 6 is extracted upward from the shaft portion mold hole 33 to obtain a molded body 1A.

  The above is one cycle of the molding method of the first embodiment, and thereafter, the punches 50, 32, 60 on the upper die 20 side and the lower die 30 side are left as they are (the lower end surface 50a of the upper punch 50 is the upper portion). As the upper end surfaces 32a, 60a of the outer lower punch 32 and the inner lower punch 60 are aligned with the upper end surface 30a of the lower die 30), the dies 20, 30 are brought close to each other again. By repeating the above process in the state of FIG. 2A, a plurality of molded bodies 1A can be obtained continuously. If the raw material P in the raw material storage unit 26 is consumed and becomes insufficient, the raw material storage unit 26 is replenished with the raw material P.

(1-3) Effects According to the molding method of the first embodiment, the raw material P stored in the raw material storage unit 26 is moved into the cavity 11 by the plunger 40 in a state where the upper punch 50 is raised and the gate 28 is opened. Then, the upper punch 50 is pushed in, the gate 28 is closed, the raw material P in the cavity 11 is subsequently compressed by the upper punch 50, and then the mold is opened to obtain the molded body 1A. By repeating this operation, the molded body 1A can be obtained continuously. Since a small amount of raw material P can be easily supplied into the cavity 11 by pushing the plunger 40 without extracting the upper punch 50, the molded body 1A can be efficiently used even if the amount of the raw material P required for one molding is small. Can be manufactured automatically.

  Further, in the filling step, first, the lower end surface on the upper die 20 side and the upper end surface on the lower die 30 side are aligned at a certain height so that no cavity is formed inside the pressing die 10. Therefore, when the upper punch 50 is driven upward from this state to open the gate 28 and inject the raw material P into the upper punch hole 27, the upper punch hole 27 is in a negative pressure state. The raw material is smoothly and rapidly injected into the inside 27.

  Next, the cavity 11 formed by driving the punches 32, 60 on the lower die 30 side downward is also in a negative pressure state. Therefore, even when the plunger 40 is pushed in and the raw material P is filled in the cavity 11, The cavity 11 is filled with the raw material P smoothly and quickly, so that the efficiency of the filling process is improved. Moreover, since the raw material P is filled in the cavity 11 in the negative pressure state, air can be prevented from remaining in the cavity 11 after the raw material is charged. As a result, the occurrence of molding defects can be suppressed, and the raw material is sufficiently filled in the thin portion, and the accuracy of the shape and dimensions is improved.

  Note that it is preferable to provide a heating means for heating the raw material P in the upper die 20 having the raw material storage portion 26 and to keep the raw material P heated by this heating means because the fluidity of the raw material P is increased. In this case, the heating temperature is set to about the softening point of the thermoplastic resin added to the binder of the raw material P. The heating means may be provided in the lower die 30 together with the upper die 20.

(1-4) Modified Example of Molding Process FIG. 5 shows a modified example of the filling process of the first embodiment. Here, the molding portion of the spur gear portion 4 is formed thicker by lowering the outer lower punch 32 further in the cavity 11 on the lower die 30 side shown in FIGS. 5C to 5D than in the case of FIG. In addition, at the stage of compression molding shown in FIG. 5 (e), the outer lower punch 32 is raised and the spur gear portion 4 is directly compressed in the axial direction. According to this form, the spur gear portion 4 can be compression-molded with a higher pressure.

  Next, second to fourth embodiments of the present invention will be described. In the drawings referred to in these embodiments, the same reference numerals are given to the same components as those in the above-described embodiments, and the description of the components may be omitted or simplified.

[2] Second Embodiment The second embodiment is another molding method for obtaining the molded body of the gear 1 shown in the first embodiment.

(2-1) Configuration of Molding Mold Device to be Used FIGS. 6A to 6E and FIGS. 7A to 7D are for molding the molded body of the gear 1 by the molding method of the second embodiment. The process is shown. First, the structure of the molding die apparatus 102 which suitably implements the molding method of the second embodiment will be described with reference to FIG.

  The upper die 20 is formed with a cylindrical gear part punch hole 22 that opens up and down. An outer upper punch 25 having a horizontal lower end surface 25a is slidable in the gear part punch hole 22 in the vertical direction. Has been inserted. As shown in FIG. 8, an inner tooth row 22 a that forms the tooth row 3 of the spur gear portion 4 of the gear 1 is formed on the inner peripheral surface of the gear portion punch hole 22. An outer tooth row 25 d is formed on the outer peripheral surface of the outer upper punch 25 so as to be slidably fitted to the inner tooth row 22 a on the inner peripheral surface of the gear portion punch hole 22.

  Inside the outer upper punch 25, a raw material reservoir 26 having a cylindrical inner peripheral surface is formed. The lower end part of the raw material storage part 26 is formed in the conical taper part 26a which tapers as it goes below. A shaft punch hole 29 that extends downward from the lower end of the taper portion 26a and opens to the lower end surface 25a is formed at the lower end portion of the outer upper punch 25. The shaft punch hole 29 is concentric with the raw material reservoir 26, and a gate 28 is formed between the shaft punch hole 29 and the raw material reservoir 26. The inner diameter of the shaft punch hole 29 is set to be equal to the diameter of the shaft portions 5 and 6 of the gear 1.

  A plunger 40 is slidably inserted into the outer upper punch 25 from an upper opening, and an inner upper punch 50 is slidably passed through the axial center of the plunger 40 along the vertical direction. When the inner upper punch 50 is lowered, the lower end portion is inserted while sliding into the shaft portion punch hole 29, and the gate 28 is opened and closed at the lower end portion of the inner upper punch 50. From the opening above the outer upper punch 25, the raw material P having plasticity is charged and stored in the raw material reservoir 26.

  A shaft die hole 33 extending in the vertical direction is formed in the lower die 30 so as to penetrate coaxially with the shaft punch hole 29 of the outer upper punch 25. The shaft portion mold hole 33 has the same diameter as the shaft portion punch hole 29, that is, the inner diameter equivalent to the diameter of the shaft portions 5 and 6 of the gear 1. A lower punch 60 is slidably inserted into the shaft mold hole 33.

(2-2) Molding Method Next, a method for molding a molded body of the gear 1 using the molding die device 102 will be described with reference to FIGS. 6 and 7. First, as shown in FIG. 6A, the lower end surface on the upper die 20 side and the upper end surface on the lower die 30 side are aligned at a certain height so that no cavity is formed inside the pressing die 10. That is, the lower end surface 20 a of the upper die 20 and the upper end surface 30 a of the lower die 30 are brought into contact with each other, and the lower end surface 25 a of the outer upper punch 25 is brought into contact with the upper end surface 30 a of the lower die 30. The lower end surface 50 a and the upper end surface 60 a of the lower punch 60 are brought into contact with each other at the same height as the contact surfaces of the upper and lower dies 20 and 30. The gate 28 in the upper die 20 is closed because the inner upper punch 50 is inserted into the shaft portion punch hole 29. Then, the raw material reservoir 26 in the outer upper punch 25 is substantially filled with the raw material P, and the tip of the plunger 40 is inserted into the raw material reservoir 26.

  Next, as shown in FIG. 6B, the inner upper punch 50 is driven upward to open the gate 28, and the raw material reservoir 26 and the shaft punch hole 29 are communicated. The shaft punch hole 29 constitutes a part of the cavity 11, and then the plunger 40 is driven downward to inject the raw material P in the material reservoir 26 into the shaft punch hole 29 from the gate 28.

  Next, as shown in FIG. 6C, while the outer upper punch 25 is driven upward and the lower punch 60 is driven downward to form the cavity 11, the plunger 40 is further lowered, The cavity 11 corresponding to the shape of the gear 1 is filled through the gate 28.

  The cavity 11 raises the outer upper punch 25 to expose the internal tooth row 22a at the lower end portion of the gear portion punch hole 22 to a height corresponding to the thickness of the spur gear portion 4, whereby the spur gear portion 4 of the gear 1 is exposed. A portion corresponding to the shaft portion 5 is formed on the upper die 20 side, and a portion corresponding to the shaft portion 6 of the gear 1 is formed on the lower die 30 side by lowering the lower punch 60. The plunger 40 is pushed into the raw material reservoir 26 and filled with the raw material P in the cavity 11.

  The filling process is completed as described above. Next, the upper punch 50 is driven downward as shown in FIG. 6D to close the gate 28, and the upper punch 50 is pushed in as shown in FIG. The raw material P in 11 is pressed and compression-molded (molding process). Thereby, the spur gear portion 4 is formed between the outer upper punch 25 and the lower die 30, and the shaft portions 5 and 6 are respectively formed in the shaft portion punch hole 29 and the shaft portion mold hole 33. Is formed.

  When the molded body 1A is formed in the pressing die 10 in this way, the extraction step shown in FIG. 7 is performed to open the pressing die 10 and extract the molded body 1A. That is, as shown in FIG. 7A, the upper die 20 is raised to expose the spur gear portion 4, and then the upper die 20 is pressed while pressing the formed body 1A with the inner upper punch 50 as shown in FIG. 7B. Then, the outer upper punch 25 is raised to expose the upper shaft portion 5. Thereafter, the entire upper die 20 side is raised as shown in FIG. 7C, and then the lower punch 60 is raised as shown in FIG. By pulling upward from the hole 33, a molded body 1A is obtained.

(2-3) Operational Effects Also by the molding method of the second embodiment, as in the first embodiment, the raw material P can be easily supplied into the cavity 11 formed in the stamping die 10 and molded efficiently. As well as being able to obtain a body, it is possible to obtain the effect of suppressing the occurrence of molding defects caused by the air remaining in the cavity 11 after filling the raw material.

  In the second embodiment, the plunger 40 and the outer upper punch 25 into which the inner upper punch 50 is inserted are set as one set, and a plurality of such sets are prepared and inserted into the upper die 20 for operation. Can be taken. According to this method, maintenance of the outer upper punch 25 into which the other set of plunger 40 and the inner upper punch 50 are inserted can be performed in parallel while the apparatus 102 is in operation. Further, the replenishment of the raw material P can be performed for each set, the operation can be prevented from stagnation due to the replenishment of the raw material P, and there is an advantage that the production efficiency is further improved.

[3] Third Embodiment FIG. 9 shows a micro gear that is a micro part obtained by sintering a molded body molded by the molding method of the third embodiment. In this gear 7, a small-diameter spur gear portion 8 having a plurality of teeth 2 formed on the outer peripheral surface is laminated on one side (upper side in FIG. 9) of the large-diameter spur gear portion 4. The shaft portion 5 protrudes from the small diameter spur gear portion 8 and the shaft portion 6 protrudes from the large diameter spur gear portion 4. Examples of the gear 7 include a dimension example in which the outer diameter D1 of the spur gear portion 4 on the large diameter side is several hundred μm to several mm, and the diameter D2 of the shaft portions 5 and 6 is several tens to several hundred μm.

(3-1) Configuration of Molding Mold Device Used FIGS. 10A to 10E and FIGS. 11A to 11D are for molding the molded body of the gear 7 by the molding method of the third embodiment. The process is shown. As shown in FIG. 10, the molding die apparatus 103 used in the molding method of the third embodiment has the same configuration on the upper die 20 side of the pressing die 10, that is, the upper die 20 and the raw material reservoir 26 inside. The outer upper punch 25, the inner upper punch 50, and the plunger 40 are configured. As shown in FIG. 12, an internal tooth row 22 a for forming the tooth row 3 of the spur gear portion 4 on the large diameter side of the gear 7 is formed on the inner peripheral surface of the lower end portion of the gear portion punch hole 22 of the upper die 20. Has been. An outer tooth row 25 d is formed on the outer peripheral surface of the outer upper punch 25 so as to be slidably fitted to the inner tooth row 22 a on the inner peripheral surface of the gear portion punch hole 22.

  On the other hand, the lower die 30 side has two lower punches 32 and 60 on the outer and inner sides as in the first embodiment, and the outer lower punch 32 is slidable in the gear portion mold hole 31 of the lower die 30. The inner lower punch 60 is slidably inserted into the shaft portion mold hole 33 of the outer lower punch 32. As shown in FIG. 12, an inner tooth row 31 a that forms the tooth row 3 of the spur gear portion 8 on the small diameter side of the gear 7 is formed on the inner peripheral surface of the upper end portion of the gear portion mold hole 31 of the lower die 30. An outer tooth row 32b is formed on the outer peripheral surface of the outer lower punch 32 so as to be slidably fitted to the inner tooth row 31a on the inner peripheral surface of the gear part mold hole 31.

(3-2) Molding Method Next, a molding method according to the third embodiment will be described with reference to FIGS. 10 and 11. First, as shown in FIG. 10A, the lower end surface on the upper die 20 side and the upper end surface on the lower die 30 side are aligned at a certain height so that no cavity is formed inside the pressing die 10. That is, the lower end surface 20 a of the upper die 20 and the upper end surface 30 a of the lower die 30 are brought into contact with each other, and the lower end surface 25 a of the outer upper punch 25 is brought into contact with the upper end surface 30 a of the lower die 30. The upper end surface 32a is brought into contact with the lower end surface 25a of the outer upper punch 25, and the lower end surface 50a of the inner upper punch 50 and the upper end surface 60a of the inner lower punch 60 are the same height as the contact surfaces of the upper and lower dies 20, 30. Now contact. The gate 28 in the upper die 20 is closed because the inner upper punch 50 is inserted into the shaft portion punch hole 29. Then, the raw material reservoir 26 in the outer upper punch 25 is substantially filled with the raw material P, and the tip of the plunger 40 is inserted into the raw material reservoir 26.

  Next, as shown in FIG. 10B, the inner upper punch 50 is driven upward to open the gate 28, and the raw material reservoir 26 and the shaft punch hole 29 are communicated. The shaft punch hole 29 constitutes a part of the cavity 11, and then the plunger 40 is driven downward to inject the raw material P in the material reservoir 26 into the shaft punch hole 29 from the gate 28.

  Next, as shown in FIG. 10 (c), the outer upper punch 25 is driven upward and the outer lower punch 32 and the inner lower punch 60 are driven downward to form the cavity 11, while further lowering the plunger 40. Then, the raw material P is filled into the cavity 11 corresponding to the shape of the gear 7 through the gate 28.

  The cavity 11 is a portion corresponding to the spur gear portion 4 and the shaft portion 6 on the large diameter side of the gear 7 by raising the outer upper punch 25 to expose the inner tooth row 22 a at the lower end portion of the gear portion punch hole 22. Is formed on the upper die 20 side, the outer lower punch 32 is lowered to expose the inner tooth row 31a at the upper end of the gear part mold hole 31, and the inner lower punch 32 is lowered to lower the small diameter side of the gear 7. Portions corresponding to the spur gear portion 8 and the shaft portion 5 are formed on the lower die 30 side. The plunger 40 is pushed into the raw material reservoir 26 and filled with the raw material P in the cavity 11.

  The filling process is completed as described above, and then, as shown in FIGS. 10D to 10E, the upper punch 50 is driven downward to press the raw material P in the cavity 11 to perform compression molding (molding process). As a result, the large diameter spur gear portion 4 and the shaft portion 6 are formed on the upper die 20 side, and the small diameter spur gear portion 8 and the shaft portion 5 are formed on the lower die 30 side. 7A is molded.

  When the molded body 7A is molded in the stamping die 10 in this way, the process proceeds to the step of extracting the molded body 7A in the same manner as in the second embodiment. That is, as shown in FIGS. 11A to 11D, the upper die 20 is raised to expose the spur gear portion 4, and the upper die 20 and the outer upper punch 25 are pressed while pressing the formed body 7 </ b> A with the inner upper punch 50. Is raised, the upper shaft portion 6 is exposed, the entire upper die 20 side is lifted, the inner lower punch 60 is raised, and the lower shaft portion 5 is extracted upward from the shaft portion mold hole 33 and molded. A body 7A is obtained.

[4] Fourth Embodiment The fourth embodiment is another molding method for obtaining the molded article of the gear 7 shown in the third embodiment.

(4-1) Configuration of Molding Device to be Used FIGS. 13A to 13E and FIGS. 14A to 14D are for molding the molded body of the gear 7 by the molding method of the fourth embodiment. The process is shown. As shown in FIG. 13, the molding die device 104 used in the molding method of the fourth embodiment is divided into two on the upper die 20 side and the lower die 30 side, respectively, like the molding die device 103 of the third embodiment. A pair of punches (outer and inner upper punches 25 and 50, outer and inner lower punches 32 and 60) are inserted, a raw material reservoir 26 is formed in the outer upper punch 25, and a plunger 40 is inserted. The configuration is different in the following points.

  The lower end portion of the gear portion punch hole 22 of the upper die 20 is reduced in diameter via a tapered portion 22b and formed in a small diameter portion 22c. Correspondingly, the outer diameter of the lower end portion of the outer upper punch 25 slidably inserted into the gear portion punch hole 22 is tapered through the taper portion 25b to form a small diameter portion 25c. The small diameter portion 25 c is slidably inserted into the small diameter portion 22 c of the gear portion punch hole 22. As shown in FIG. 15, an inner tooth row 22 d for forming the tooth row 3 of the spur gear portion 8 on the small diameter side of the gear 7 is formed on the inner peripheral surface of the small diameter portion 22 c on the upper die 20 side. An outer tooth row 25d that is slidably fitted to the inner tooth row 22d of the upper die 20 is formed on the outer peripheral surface of the small-diameter portion 25c of the outer upper punch 25.

  The lower die 30 is formed with a gear part mold hole 31 having an inner diameter corresponding to the outer diameter of the spur gear part 4 on the large diameter side of the gear 7, and the outer lower punch 32 is slid into the gear part mold hole 31. It is inserted freely. As shown in FIG. 15, an inner tooth row 31 a that forms the tooth row 3 of the spur gear portion 4 is formed on the inner circumferential surface of the upper end portion of the gear portion mold hole 31, and the outer circumferential surface of the outer lower punch 32. Is formed with an external tooth row 32b slidably fitted into the internal tooth row 31a of the gear part mold hole 31.

(4-2) Molding Method Next, a molding method according to the fourth embodiment will be described with reference to FIGS. 13 and 14. First, as shown in FIG. 13A, the lower end surface on the upper die 20 side and the upper end surface on the lower die 30 side are aligned at a certain height so that no cavity is formed inside the pressing die 10. That is, the lower end surface 20 a of the upper die 20 and the upper end surface 30 a of the lower die 30 are brought into contact with each other, and the upper end surface 32 a of the outer lower punch 32 is brought into contact with the lower end surface 20 a of the upper die 20. The upper end surface 25 a is brought into contact with the upper end surface 32 a of the outer lower punch 32, and the lower end surface 50 a of the inner upper punch 50 and the upper end surface 60 a of the inner lower punch 60 are the same height as the contact surfaces of the upper and lower dies 20, 30. Now contact. The gate 28 in the upper die 20 is closed because the inner upper punch 50 is inserted into the shaft portion punch hole 29. Then, the raw material reservoir 26 in the outer upper punch 25 is substantially filled with the raw material P, and the tip of the plunger 40 is inserted into the raw material reservoir 26.

  Next, as shown in FIG. 13B, the inner upper punch 50 is driven upward to open the gate 28, and the raw material reservoir 26 and the shaft punch hole 29 are communicated. The shaft punch hole 29 constitutes a part of the cavity, and then the plunger 40 is driven downward to inject the raw material P in the raw material reservoir 26 from the gate 28 into the shaft punch hole 29.

  Next, as shown in FIG. 13C, the outer upper punch 25 is driven upward, and the outer lower punch 32 and the inner lower punch 60 are driven downward to form the cavity 11, while further lowering the plunger 40. Then, the raw material P is filled into the cavity 11 corresponding to the shape of the gear 7 through the gate 28.

  The cavity 11 has a portion corresponding to the spur gear portion 8 and the shaft portion 5 on the small diameter side of the gear 7 by raising the outer upper punch 25 to expose the inner tooth row 22 a at the lower end portion of the gear portion punch hole 22. Formed on the upper die 20 side, the outer lower punch 32 is lowered to expose the inner tooth row 31a at the upper end of the gear part mold hole 31, and the inner lower punch 32 is lowered to lower the large diameter side of the gear 7. Portions corresponding to the spur gear portion 4 and the shaft portion 6 are formed on the lower die 30 side. The plunger 40 is pushed into the raw material reservoir 26 and filled with the raw material P in the cavity 11.

  Thus, the filling process is completed, and then, as shown in FIGS. 13D to 13E, the upper punch 50 is driven downward to press the raw material P in the cavity 11 to perform compression molding (molding process). Thus, the small-diameter side spur gear portion 8 and the shaft portion 5 are formed on the upper die 20 side, and the large-diameter side spur gear portion 4 and the shaft portion 6 are formed on the lower die 30 side. 7A is molded.

  When the molded body 7A is formed in the pressing die 10 in this way, the process proceeds to the extraction step. That is, as shown in FIGS. 14A to 14D, the upper die 20 is raised to expose the spur gear portion 4, and the upper die 20 and the outer upper punch 25 are pressed while pressing the formed body 7 </ b> A with the inner upper punch 50. Is raised, the upper shaft portion 5 is exposed, the entire upper die 20 side is raised, the inner lower punch 60 is raised, and the lower shaft portion 6 is extracted upward from the shaft portion mold hole 33 and molded. A body 7A is obtained.

[5] About 3rd Embodiment and 4th Embodiment According to the said 3rd Embodiment and 4th Embodiment, the gear with a shaft of the two-step structure which has the spur gear parts 4 and 8 of large diameter and small diameter coaxially. 7A can be obtained. In these embodiments as well, as in the second embodiment, it is possible to easily supply the raw material P into the pressing die 10 and to obtain a molded body efficiently, and air remains in the cavity 11 after the raw material is filled. In the same manner, the effects of suppressing the occurrence of molding defects due to the above, and maintaining a plurality of sets of outer upper punches 25 into which the plunger 40 and the inner upper punch 50 are inserted, and improving the efficiency of replenishing the raw material P are obtained in the same manner. be able to.

  DESCRIPTION OF SYMBOLS 1A, 7A ... Molded object, 11 ... Cavity, 20 ... Upper die, 20a ... Lower end surface of upper die, 22 ... Gear part punch hole, 25 ... Outer upper punch, 26 ... Raw material storage part, 27 ... Upper punch hole, 28 DESCRIPTION OF SYMBOLS ... Gate, 29 ... Shaft punch hole, 30 ... Lower die, 30a ... Upper end surface of lower die, 31 ... Gear part die hole, 32 ... Outer lower punch, 33 ... Shaft die hole, 40 ... Plunger, 50 ... Upper Punch, inner upper punch, 60 ... lower punch, inner lower punch, 101, 102, 103, 104 ... molding tool, P ... raw material.

Claims (3)

A lower die having a mold hole;
An upper die in which a lower end surface is abuttable with an upper end surface of the lower die and a punch hole opened in the lower end surface is formed in the lower end portion ;
A lower punch that is slidably fitted into the mold hole of the lower die,
An upper punch that is slidably fitted into the punch hole of the upper die,
A raw material having plasticity formed by communicating with the punch hole above the punch hole in the upper die, and adding 30 to 60% by volume of a binder made of a thermoplastic resin and wax to the metal powder, followed by heating and kneading. A raw material storage part for storing ;
The plastic raw material, which is slidably inserted into the raw material storage part and stored in the raw material storage part, is injected into the cavity formed from the lower die, the upper die and the lower punch through the punch hole. A plunger,
The upper punch is slidably penetrated in the plunger along the sliding direction of the plunger and reciprocally slides to form a gate formed between the raw material reservoir and the punch hole. When opening and closing and sliding in the cavity direction, using a molding die apparatus provided to close the gate and compress the plastic material in the cavity into a molded body,
In a state where the upper end surface of the lower die, the lower end surface of the upper die, the lower end surface of the upper punch, and the upper end surface of the lower punch are aligned,
The upper punch is driven to open the gate, the plunger is driven to inject a plastic material from the gate into the punch hole, and then at least one of the upper punch and the lower punch is driven. While forming the cavity, the plunger is further driven to fill the cavity with a plastic raw material through the gate; and
Molding that compresses the plastic material in the cavity into a compact by driving the upper punch to close the gate and pressing the plastic material after filling the cavity with plastic material. Process,
Extracting the molded body from the mold hole; and
A method of forming a raw material having plasticity, characterized by comprising:   2. The method for molding a raw material having plasticity according to claim 1, wherein in the molding step, the lower punch is driven together with the upper punch to compress the plastic raw material in the cavity into a molded body.   The at least one of the upper punch and the lower punch is composed of a plurality of punches, and in the filling step, the filling step is started from a state in which end faces of all the punches are aligned. A method for forming a raw material having plasticity.

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