JP2006015397A - Method of driving die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of driving a die, which restrains the occurrence of cracking in a compact produced by powder molding. <P>SOLUTION: In the method of driving the die, the compact 38 is produced with an upper punch 34, a first lower punch 24, a second lower punch 26 and a frame mold 28 in cooperation. After the compact 38 has been produced, the frame mold 28 is lowered and the leg 42 of the compact 38 is taken out from a through hole 29 of the frame mold 28. Then a cope is separated from the compact 38. Finally, the compact 38 placed on the top face of the frame mold 28 is raised by lifting the frame mold 28 so that the compact 38 is separated from the first lower punch 24 and the second lower punch 26. Internal stress is less liable to concentrate in the root 42a of the leg 42 of the compact 38 by driving the die (upper punch 34, first lower punch 24, second lower punch 26 and frame mold 28) in the above order, so that the occurrence of cracking in the root 42a is deliberately restrained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for driving a mold used in a powder metallurgy press apparatus.

  As a powder metallurgical press apparatus for pressing a raw material powder to obtain a molded body, a press apparatus using a withdrawal method is known (for example, Patent Document 1 below). Such a pressing apparatus is shown in detail in FIG. 22 of Non-Patent Document 1 below.

  The procedure for producing a powder compact using the apparatus disclosed in this document will be described with reference to FIGS. FIGS. 3 (a) to 7 (a) are diagrams showing a procedure for driving a mold of a conventional apparatus when producing a powder compact, and FIGS. 3 (b) to 7 (b) It is a principal part enlarged view of the conventional apparatus at the time. The powder compact 46 produced by this procedure is a so-called pot-type ferrite core, and has a low profile (thin) and a foot 48.

  As shown in FIGS. 3 to 7, the conventional apparatus 50 includes a first lower mold 52 corresponding to the foot 48 of the powder molded body 46, a second lower mold 54 corresponding to the remaining area 49 of the foot 48, and a die. A frame mold 58 and an upper mold 60 fixed to the plate 56 are provided. When the powder compact 46 is manufactured, first, a cavity C is formed by the frame mold 58 and the first and second lower molds 52 and 54, and the raw material powder 62 is filled in the cavity C (see FIG. 3).

  Next, the upper mold 60 is inserted into the cavity C, and the raw material powder 62 is pressed to form the powder compact 46 (see FIG. 4). Thereafter, the frame mold 58 and the second lower mold 54 are lowered simultaneously, and the powder compact 46 is extracted from the frame mold 58. That is, the frame mold 58 is lowered to a position where the upper surface position of the frame mold 58 and the upper end position of the first lower mold 52 are the same (see FIG. 5). The second lower mold 54 is performed by the cooperation of a wedge part 64 that moves up and down integrally with the die plate to which the frame mold 58 is attached, and a roller 66 that is in contact with the slope of the tip of the wedge part 64. .

  Finally, the upper mold 60 is lifted (see FIG. 6), and the frame mold 58 is lifted while maintaining the height positions of the first and second lower molds 52 and 54 (see FIG. 7) to complete. The powder compact 46 is taken out from the device 50.

JP 2001-287098 A Powder metallurgy press term (JPMA G01-1995), Japan Powder Metallurgy Association, 1995, P31

  However, the powder molded body 46 produced by such a conventional mold driving method has a problem that cracks are likely to occur in the base portion 48a of the foot 48. The inventors have found that the occurrence of such cracks is caused by the expansion (spring back) of the powder compact 46. That is, as shown in FIG. 5, when the second lower mold 54 is lowered, the powder molded body 46 is in a state where the spring back is restricted only by the upper mold 60 and the first lower mold 52. At this time, the powder molded body 46 expands toward the gap generated by the lowering of the second lower mold 54, and as a result, internal stress concentrates on the base portion 48 a of the foot 48 of the powder molded body 46, A crack occurs in the portion 48a.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a mold driving method in which the occurrence of cracks in a powder molded body is suppressed.

  The mold driving method according to the present invention is a press molding apparatus for producing a powder molded body having a foot portion provided on the main surface, and has a through hole, and the side surface of the powder molded body is formed by the side surface of the through hole. A mold for molding the first mold, a first lower mold corresponding to the foot portion of the main surface of the powder molded body, and one side of the through hole. The second lower mold corresponding to the remaining region of the foot portion of the main surface of the powder molded body and the other side of the through hole can be inserted into the through hole. A mold driving method applied in a press molding apparatus provided with an upper mold for molding the upper surface of a powder molded body, wherein the first and second are in the through holes of the frame mold set at the reference position. A step of filling the raw powder in the cavity defined by placing the lower mold and the upper mold in the cavity And press the raw material powder in the cavity to obtain a powder compact from the raw material powder, while maintaining the height position of the first and second lower molds, the frame mold from the reference position, Lowering the upper surface position of the frame mold to the position where the upper end position of the first lower mold is the same, extracting the legs of the powder molded body from the through hole, and raising the upper mold after lowering the frame mold And a step of separating the upper mold from the powder molded body and a step of lifting the frame mold to a reference position and separating the first and second lower molds from the powder molded body.

  In this mold driving method, a powder molded body is produced by cooperation of the upper mold and the first and second lower molds. That is, a powder compact is produced by pressing the raw material powder in the cavity defined by the frame mold and the first and second lower molds with the upper mold. And after producing a powder compact, a frame type | mold is lowered | hung and the leg part of a powder compact is extracted from the through-hole of a frame type | mold. At this time, the foot of the powder molded body expands, and the powder molded body is placed on the upper surface of the frame mold. Next, the upper mold is released from the powder compact. Finally, by raising the frame mold, the powder molded body placed on the upper surface of the frame mold is raised, and the powder molded body is separated from the first and second lower molds. When the molds (upper mold, first and second lower mold, frame mold) are driven in this order, when the upper mold is separated from the powder molded body, the powder molded body expands upward, and the molded body Internal internal stress is relieved. Therefore, even if the first lower mold is subsequently separated from the powder molded body, the powder molded body hardly expands toward the gap with the first lower mold. Therefore, according to this mold driving method, it is difficult for internal stress to concentrate on the base portion of the foot portion of the powder molded body, and the occurrence of cracks in that portion is significantly suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the drive method of the metal mold | die with which generation | occurrence | production of the crack in a powder compact was suppressed is provided.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments that are considered to be the best for carrying out a mold driving method according to the present invention will be described below in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected about the same or equivalent element, and the description is abbreviate | omitted when description overlaps.

  First, prior to the description of the mold driving method according to the present embodiment, a press molding apparatus to which the mold driving method is applied will be described. FIG. 1 is a schematic cross-sectional view showing a press forming apparatus 10 according to the present embodiment.

  As shown in FIG. 1, the press molding apparatus 10 includes a base plate 12. On the base plate 12, a punch presser base 14 is provided. A plurality of sliding blocks 16 are slidably mounted on the upper surface of the base plate 12 around the punch presser base 14. The sliding block 16 is provided with rollers 18 extending in the surface direction of the base plate 12, and the rollers 18 are controlled by a control unit (not shown). In addition, a block 20 is mounted on each end of the sliding block 16 on the punch presser base 14 side.

  Further, a holder 22 is supported above the punch presser base 14 while being lifted from the punch presser base 14 by a lift mechanism (for example, a spring support mechanism) (not shown). The holder 22 is supported so as to float at a position spaced apart from the base plate 12 by a predetermined distance, and can move to some extent by an external force. When the holder 22 moves downward, the lower surface of the holder 22 comes into contact with the block 20 mounted on the sliding block 16, so that the downward movement of the holder 22 is restricted by the block 20. In addition, a lower mold attachment plate 23 is provided on the holder 22.

  Further, a pair of flat lower first punches (first lower molds) 24 facing each other are erected on the punch presser base 14, and the above-described holder 22 and lower mold mounting plate 23 are arranged on the lower side. It is inserted through one punch 24. Further, a lower second punch (second lower mold) 26 sandwiched between a pair of lower first punches 24 is erected on the lower mold attaching plate 23.

  Above the base plate 12, a die plate 30 facing the base plate 12 and sandwiching the frame mold 28 is supported in a floating state by a support mechanism (not shown). A wedge 32 extending in the direction of the base plate 12 is provided at a portion of the die plate 30 corresponding to each position of the roller 18 provided on the sliding block 16. The portion of the wedge tip 32a that contacts the roller moves so that the sliding block 16 moves away from the punch presser base 14 (in the direction of arrow A in FIG. 1) when the wedge 32 contacts the roller 18. It is chamfered diagonally. That is, by rotating the roller 18 of the sliding block 16 in a predetermined direction, the sliding block 16 slides on the base plate 12 in a direction away from the punch presser base 14, and the die plate 30 and the frame mold 28 are lowered.

  The frame mold 28 described above extends in the thickness direction of the die plate 30 and has a cross-sectional shape that combines the shape of the upper end surface of the lower first punch 24 and the shape of the upper end surface of the lower second punch 26. A hole 29 is formed. The lower first punch 24 and the lower second punch 26 extend to the inside of the through hole 29 and close the through hole 29 from the lower side of the through hole 29.

  Further, an upper punch (upper die) 34 facing the die plate 30 and having substantially the same cross-sectional shape as the through-hole 29 is disposed above the die plate and corresponding to the through-hole 29. Has been. The upper punch 34 is supported by an upper punch plate (not shown) via an upper punch receiving plate 36. The upper punch plate extends in parallel with the die plate 30 and is driven in a direction to advance and retreat with respect to the die plate 30 by a drive mechanism (not shown). That is, the upper punch 34 that moves integrally with the upper punch plate can also move in a direction (arrow B direction) that moves forward and backward with respect to the die plate 30.

  That is, in the press molding apparatus 10, the upper punch 34 can move in a direction to advance and retreat with respect to the base plate 12 (see arrow B in FIG. 1). Further, the lower second punch 26 that moves integrally with the holder 22 also floats in a direction to advance and retreat with respect to the base plate 12 (see arrow C in FIG. 1). On the other hand, the lower first punch 24 does not move relative to the base plate 12. Further, the frame mold 28 can move in a direction to advance and retreat with respect to the base plate 12 by the rotation of the roller 18 (see arrow D in FIG. 1).

  The lower first punch 24 and the lower second punch 26 can be inserted into the through hole 29 from below the through hole 29 of the frame mold 28, and the upper punch 34 is inserted into the through hole of the frame mold 28. 29 can be inserted into the through-hole 29 from above.

  A procedure for producing a powder compact using the press molding apparatus 10 described above will be described with reference to FIG. FIG. 2 is a diagram showing a procedure for producing a powder compact in the present embodiment.

  When producing the powder compact 38, first, the lower first punch 24 and the lower second punch 26 are disposed in the through hole 29 of the frame mold 28, and the frame mold 28, the lower first punch 24 and the lower second punch 28 are disposed. A cavity C is defined by the punch 26, and the raw material powder (ferrite powder) 40 of the powder compact 38 is filled in the cavity C (see FIG. 2A). At this time, the upper surface position S1 of the frame mold 28 is the reference position (P1).

  Next, the upper punch plate is driven by the above-described drive mechanism to lower the upper punch 34, insert the upper punch 34 into the through hole 29, and press-mold the raw material powder 40 (see FIG. 2B). ). By this press molding process, a powder molded body 38 having a body portion 41 and a foot portion 42 is obtained. That is, the side surface of the powder molded body 38 is molded by the side surface 29a of the through hole 29 of the frame mold 28, and the foot portion 42 extending from the main surface 41a of the body portion 41 of the powder molded body 38 is molded by the lower first punch 24. The remaining area 44 of the foot portion 42 in the main surface 41 a of the body portion 41 is formed by the lower second punch 26, and the upper surface of the powder compact 38 is formed by the upper punch 34. At this time, the upper surface position S1 of the frame mold 28 is lowered from the reference position (P1) to the press molding position (P2) due to friction between the frame mold 28 and the upper punch 34. Further, the lower second punch 26 is lowered to a position regulated by the block 20 on the sliding block 16 by the press pressure.

  After the powder compact 38 is formed, the sliding block roller is rotated to pull down the frame mold 28 fixed to the die plate (see FIG. 2C). At this time, the upper surface position S1 of the frame mold 28 is lowered from the press molding position (P2) to a position (P3) that is the same as the upper end position S2 of the lower first punch 24. Thereby, the powder compact 38 is extracted from the through hole 29 of the frame mold 28. When the powder compact 38 is extracted from the through hole 29, the foot portion 42 of the powder compact 38 slightly expands, and the powder compact 38 is placed on the upper surface of the frame mold 28.

  Thereafter, the upper punch plate is driven by the drive mechanism to raise the upper punch 34 and release the upper punch 34 from the powder compact 38 (see FIG. 2D). Finally, the roller 18 of the sliding block 16 is rotated to push up the frame 28 (see FIG. 2 (e)). As a result, the powder compact 38 is also raised together with the die plate 30, and the lower first punch 24 and the lower second punch 26 are separated from the powder compact 38. At this time, the upper surface position S1 of the frame mold 28 rises from the position (P3) that is the same as the upper end position S2 of the lower first punch 24 to the reference position (P1).

  As described in detail above, in the method of driving the mold (upper punch 34, lower first punch 24, lower second punch 26, frame mold 28) according to the present embodiment, the powder compact 38 is a frame mold. When extracted from 28, no gap is formed between the powder compact 38 and the lower second punch 26 (see FIG. 2C). Since the upper punch 34 is separated from the powder molded body 38 before the lower second punch 26 (see FIG. 2D), the powder molded body 38 expands upward when the upper punch 34 is raised, The internal stress inside the molded body is relieved. Therefore, even if the lower second punch 26 is separated from the powder molded body 38 thereafter, the powder molded body 38 hardly expands in the gap between the powder molded body 38 and the lower second punch 26.

  Therefore, after the lower second punch 26 is separated from the powder compact 38, the situation in which internal stress concentrates on the root portion 42a of the foot portion 42 of the powder compact 38 is significantly suppressed. Therefore, the occurrence of cracks at the base portion 42a of the foot portion 42 is suppressed.

  The present invention is not limited to the above embodiment, and various modifications are possible. For example, the powder compact is not limited to a pot-type ferrite core, and may be various shapes of powder compacts having feet.

It is the schematic sectional drawing which showed the powder metallurgy press apparatus which concerns on embodiment of this invention. It is the figure which showed the procedure which produces a powder compact using the powder metallurgy press apparatus of FIG. (A) is a schematic sectional drawing which showed the state of the metal mold | die of the conventional apparatus at the time of producing a powder compact, (b) is a principal part enlarged view of (a). (A) is a schematic sectional drawing which showed the state of the metal mold | die of the conventional apparatus at the time of producing a powder compact, (b) is a principal part enlarged view of (a). (A) is a schematic sectional drawing which showed the state of the metal mold | die of the conventional apparatus at the time of producing a powder compact, (b) is a principal part enlarged view of (a). (A) is a schematic sectional drawing which showed the state of the metal mold | die of the conventional apparatus at the time of producing a powder compact, (b) is a principal part enlarged view of (a). (A) is a schematic sectional drawing which showed the state of the metal mold | die of the conventional apparatus at the time of producing a powder compact, (b) is a principal part enlarged view of (a).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Powder metallurgy press apparatus, 24 ... Lower first punch, 26 ... Lower second punch, 28 ... Frame type, 34 ... Upper punch, 38 ... Powder compact, 41a ... Main surface, 42 ... Foot, 42a ... Base Part 44: Residual region 40 Raw material powder C Cavity P1, P2, P3 Position S1 Frame top surface position S2 Bottom first punch top surface position

Claims (1)

A press molding apparatus for producing a powder molded body provided with a foot on a main surface,
A frame mold having a through hole, and molding the side surface of the powder molded body by the side surface of the through hole;
A first lower mold provided so as to be able to be inserted into the through hole from one side of the through hole, and corresponding to the foot portion of the main surface of the powder molded body;
A second lower mold provided so as to be able to be inserted into the through hole from the one side of the through hole, and corresponding to a remaining area of the foot portion of the main surface of the powder molded body;
A mold driving method applied in a press molding apparatus provided so as to be able to be inserted into the through hole from the other side of the through hole, and an upper mold for molding the upper surface of the powder molded body,
Filling the raw material powder into a cavity defined by disposing the first and second lower molds in the through holes of the frame mold set at a reference position;
Inserting the upper mold into the cavity, pressing the raw material powder in the cavity, and obtaining the powder compact from the raw material powder;
In the state where the height positions of the first and second lower molds are held, the upper surface position of the frame mold and the upper end position of the first lower mold are the same from the reference position. Lowering to a position and extracting the foot part of the powder compact from the through hole;
After lowering the frame mold, raising the upper mold and releasing the upper mold from the powder compact;
A step of raising the frame mold to the reference position and separating the first and second lower molds from the powder compact.

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