JP2510213Y2 - Mold for green compact - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention forms a cavity with a plurality of mold members,
The present invention relates to a green compact molding die for compressing the powder in the cavity to form a green compact, and particularly to a die for molding a green compact with holes.

2. Description of the Related Art A powder compacting die for compressing powder in a cavity to form a powder compact is described in, for example, "Knowledge of Materials" (published by Toyota Motor Corporation), pages 32 to 33. As is widely known. This mold comprises (a) a lower punch, (b) a die which is disposed outside the lower punch, and which is relatively movable in the axial direction with respect to the lower punch, and (c) facing the lower punch. A cavity is formed by a plurality of mold members including a lower punch and an upper punch that can be relatively approached and separated from each other, and metal powder such as iron, copper, nickel, etc., alone or mixed in the cavity. After being filled and filled, the lower punch and the upper punch are brought relatively close to each other, whereby the powder is compressed and the green compact is molded.

When molding a green compact having a through hole in the center, the mold member is configured to further include (d) a core rod, and the lower punch is fitted to the outside of the core rod so as to be relatively movable in the axial direction. To be done. The clearance at the fitting portion between the lower punch and the core rod is very small, about 0.01 to 0.03 mm, and the misalignment between the lower punch and the core rod is prevented. After the molding is completed, the lower punch and the upper punch are separated from each other, and the lower punch and the core rod and the die are relatively moved, so that the green compact having a through hole having the same diameter as the core rod is extracted from the die and the core rod. .

In this case, depending on the shape of the green compact, the lower punch may be provided with a portion whose outer peripheral surface defines a part of the cavity. For example, as shown in FIG. 6, an annular protrusion formed on the lower punch 200 along the outer peripheral surface 204 of the core rod 202.
206 may be formed.

The problem to be solved by the invention And, in the mold as described above, there is a problem that so-called galling is likely to occur in the core rod during the compacting process. When the lower punch and the upper punch come close to each other to compress the powder, the portion defining a part of the cavity of the lower punch is reduced in diameter by the pressure to the outer peripheral surface side thereof. The diameter part directly tightens the core rod,
When the clearance is large, the core rod is tightened through the powder that has entered the gap, and in this state, the lower punch and the core rod move relative to each other in the axial direction, which causes galling. For example, in the example of FIG. 6, the annular projection 206 of the lower punch 200 and the portion in the vicinity thereof have a reduced diameter, and the core rod 202 is likely to be galled. When the galling occurs, the core rod and the lower punch cannot move smoothly relative to each other, the green compact cannot be molded well, and the life of the core rod is shortened.

This problem is particularly likely to occur when an annular protrusion is formed on the punch, but depending on the shape of the green compact to be molded, the entire lower punch has a relatively thin cylindrical shape, and a part of the outer peripheral surface is formed. May define a portion of the cavity, again causing similar problems.

If the clearance between the lower punch and the core rod is increased, the core rod will not be tightened not only when the diameter of the lower punch is reduced but also through the powder, but in the radial direction between the lower punch and the core rod. However, there is a problem that the accuracy of the product is deteriorated due to the misalignment between the two and the misalignment between them.

In view of the above problems, the present invention causes galling or seizure between the lower punch and the core rod due to the intrusion of powder into the fitting portion between the lower punch and the core rod or the reduced diameter of the lower punch. It is an object of the present invention to obtain a die for compacting a powder compact that can prevent such a situation and can prevent misalignment between the lower punch and the core rod.

Means for Solving the Problems And the gist of the present invention is (a) core rod, (b)
A lower punch which is fitted to the outside of the core rod so as to be relatively movable in the axial direction, and (c) is arranged outside the lower punch,
A cavity is formed by a plurality of mold members including a die movable axially relative to the lower punch, and (d) an upper punch that is provided so as to face the lower punch and can relatively approach and separate from the lower punch. In a powder compact molding die having a lower punch having an outer peripheral surface that defines a part of a cavity, a fitting portion between the lower punch and the core rod is first, second and third fitted in order from the cavity side. The clearance of the first fitting portion is made larger than that of the third fitting portion, and the clearance of the second fitting portion is further increased.

The clearance between the lower punch and the core rod is
The clearance between the inner peripheral surface of the fitting hole and the outer peripheral surface of the core rod may be made different by making the inner diameter of the fitting hole of the lower punch different in three steps. Further, by changing the outer diameter of the core rod in three steps, or by changing both the outer diameter of the core rod and the inner diameter of the fitting hole of the lower punch in two or more steps, the outer peripheral surface of the core rod and the lower punch are fitted. The clearance from the inner peripheral surface of the dowel may be different. In this case, the relative length between the lower punch and the core rod changes the axial length of any of the first, second, and third fitting portions. It doesn't matter.

Effect In the powder compact molding die configured as described above, when the powder is filled in the cavity, the powder enters the first fitting portion between the lower punch and the core rod. The body passes through the first fitting portion and drops into the second fitting portion. Even if the powder stays in the first fitting portion, the clearance in the first fitting portion is larger than the clearance between the lower punch and the core rod in the related art, so that the powder is not left in the first fitting portion. It does not stay at a high density. Further, the clearance of the second fitting portion is made larger than the clearances of the first and third fitting portions, and the clearance of the third fitting portion is the smallest, so that the powder dropped from the first fitting portion It is accommodated in the second fitting portion, and it is possible to favorably avoid passing through the step portion between the second fitting portion and the third fitting portion and reaching the third fitting portion.

After the powder is filled in the cavity, the lower punch and the upper punch are relatively brought close to each other to compress the powder in the cavity and form a green compact. Since the lower punch and the core rod are configured to move relative to each other by being guided by the third fitting portion, the lower punch and the core rod are not misaligned. As the powder is compressed, the diameter of the part that defines a part of the cavity of the lower punch is reduced, but the clearance of the first fitting part corresponding to the fitting part of this part is increased to some extent, so the lower punch and the core rod. But of course
Since the core rod is not tightened through the powder, seizure can be well avoided. In addition, since the second fitting portion having a large clearance is formed between the first fitting portion and the third fitting portion, the third fitting portion is reduced by the reduction in diameter of the first fitting portion. The diameter amount is reduced, and the third fitting portion is also prevented from tightening the core rod. Further, since the axial length of the first fitting portion is shortened by forming the second fitting portion, the occurrence of seizure can be avoided even better.

As described above, according to the present invention, the core rod is prevented from being misaligned while preventing the misalignment between the lower punch and the core rod by a simple means of changing the clearance of the fitting portion between the lower punch and the core rod in three steps. It is possible to avoid galling and seizure, to prolong the life of the core rod and to reduce the cost of the device. In addition, since the lower punch and the core rod slide accurately and smoothly, the compacting accuracy of the green compact is increased and the productivity is improved.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

In FIGS. 1 to 3, 10 is a base plate. The base plate 10 is supported by a lower ram (not shown) and can be moved up and down as the lower ram moves up and down. There are multiple guide bars on the base plate 10.
One end of 12 (two shown in the figure) is fixed, and the other end of the guide bar 12 is fixed to a die holder 14 provided above the base plate 10. Therefore, the base plate 10 and the die holder 14 move integrally. A punch plate 16 is arranged between the base plate 10 and the die holder 14. The punch plate 16 is slidably fitted to the guide bar 12, and is immovably fixed to a support member (not shown).

The core supporter 20 is attached to the retainer 22 on the base plate 10.
It is fixed by. The core supporter 20 extends parallel to the moving direction of the base plate 10, and a core rod 24 is coaxially attached to the upper end surface thereof. Core rod 24
A female screw hole (not shown) is formed on the lower end surface of the core supporter 20, and a male screw portion protruding from the upper end surface of the core supporter 20 is screwed into the hole to attach the core supporter 20 to the core supporter 20 in a replaceable manner. is there.

A first lower punch 26 is attached to the punch plate 16 so as to be vertically movable. The lower end of the first lower punch 26 is fixed to a support base 27, and the support base 27 includes the punch plate 16
A plurality of air cylinders 28 (two of which are shown in the figure) attached to the respective air cylinders 28 are vertically movably supported by guide rods 29 extending from the air cylinders 28, respectively. Therefore, the operation of the air cylinder 28 causes the first lower punch 26 to move axially relative to the core rod 24. The air cylinder 28 is of a double-acting type, and when the air is supplied to the first chamber 30, the first lower punch 26 moves up, and when the air is supplied to the second chamber 31, it moves down.

A fitting hole 32 is formed in the central portion of the first lower punch 26, and the core rod 24 is fitted in the fitting hole 32 so as to be relatively movable. As is clear from FIG. 4, the fitting hole 32 is formed from the upper end side of the first lower punch 26 to the first fitting hole portion 34,
It is composed of the second fitting hole portion 36, the third fitting hole portion 38, and the escape hole portion 40. Of the three fitting hole portions excluding the escape hole portion 40, the diameter of the second fitting hole portion 36 is Largest, third fitting hole
38 has the smallest diameter. As a result, the clearance (A shown in FIG. 4) of the fitting portion (referred to as the first fitting portion) 42 between the first fitting hole portion 34 and the core rod 24 is 0.03 to 0.05.
mm, the clearance (B) of the fitting portion (referred to as the second fitting portion) 44 between the second fitting hole portion 36 and the core rod 24 is 0.3 to 0.5 mm,
The clearance (C) of the fitting portion (referred to as the third fitting portion) 46 between the third fitting hole portion 38 and the core rod 24 is 0.01 to 0.03 mm. In addition, these first to third fitting hole portions 42, 44,
The axial length of each 46 is about 8 mm.

The upper end surface of the first lower punch 26 is a substantially horizontal mold surface 50, and an annular projection 52 surrounding the outer peripheral surface of the core rod 24 is formed around the fitting hole 32. The protrusion 52 is chamfered.

A second lower punch 70 is fitted on the outer peripheral surface of the first lower punch 26. The second lower punch 70 has a cylindrical shape, and an upper end surface thereof is a mold surface 72. A flange portion 73 is formed at the lower end of the second lower punch 70, and is fixed to the support base 76 by a retainer 74 at the flange portion 73. The support base 76 is fixed to the punch plate 16 via a support member 78.

A die 80 is fitted on the outer peripheral surface of the second lower punch 70. The die 80 has a cylindrical shape, and the inner peripheral surface thereof is a mold surface 82. It is held on the outer peripheral surface by the die holder 14 and is movable in the axial direction relative to the first lower punch 26 by the movement of the die holder 14.

A first upper punch 86 (see FIG. 2) is arranged above the first lower punch 26. The first upper punch 86 has a mold surface 88 facing the mold surface 50 of the first lower punch 26, and the mold surface 88 has a protrusion.
A protrusion 90 having the same shape as 52 is formed. The first upper punch 86 is supported by an upper ram (not shown) and is moved up and down as the upper ram moves in the vertical direction to approach the first lower punch 26.
Be separated. A second upper punch 92 is fitted on the outer peripheral surface of the first upper punch 86. The second upper punch 92 has a mold surface 94 facing the mold surface 72 of the second lower punch 70, and is supported by the upper ram via a cushion device (not shown).

In the present embodiment, the mold surface 50 of the first lower punch 26,
Mold surface 72 of second lower punch 70, mold surface 82 of die 80, first upper punch
The mold surface 88 of 86 and the mold surface 94 of the second upper punch 92 form a cavity 100. The first lower punch 26, the second lower punch 70, the die 80, the first upper punch 86, the second upper punch 90, etc. are a plurality of mold members that form the cavity 100. The outer peripheral surfaces of the protrusion 52 and the protrusion 90 of the first upper punch 86 define a part of the cavity 100.

A plate-shaped cam 104 is attached to the die 80.
The cam 104 extends parallel to the axial direction of the core rod 24,
A cam surface 106 is formed at the tip. On the other hand, a block 108 is provided on the punch plate 16 so as to be movable in the radial direction of the core rod 24.
A cam follower 110 that can contact 06 is attached. As shown in FIG. 2, the block 108 has a contact surface 114 that can contact the lower end surface 112 of the support base 27 that supports the first lower punch 26. In the original position, the contact surface 114 of the block 108 contacts the lower end surface 112 of the support base 27 to define the lowering limit of the first lower punch 26, but the die 80 lowers as the lower ram lowers. Then, the cam surface 106 of the cam 104 comes into contact with the cam follower 110, and the die 80 is further lowered to move the block 108 to the retracted position where it does not come into contact with the lower end surface 112, as shown in FIG. The first lower punch 26 is allowed to descend.

In the green compact molding die configured as described above,
In the non-actuated state of the mold, as shown in FIG. 1, the air is supplied to the first chamber 30 of the air cylinder 28 to raise the first lower punch 26 to the rising end position, The upper part of the lower punch 26 is projected from the second lower punch 70, the lower ram is also raised to the top dead center, and the die 80 is stopped at the position farthest from the punch plate 16. The upper ram is also raised, and the first and second upper punches 86, 92 are located in the raised position.

In this state, the powder 120 is filled in the cavity 100. The powder 120 is a mixture of iron [Fe] with 2% of copper [Cu], 0.5% of graphite [Gr] and 0.8% of zinc stearate [Zn (C ₁₇ H ₃₅ COO) ₂ ] as a lubricant. Powder 1
As the 20 is filled, the powder is put in the fitting hole 32 of the first lower punch 26.
Although 120 may enter, the clearance of the first fitting portion 42 on the side of the cavity 100 is larger than that of the conventional one, and therefore most of the powder 120 passes through the first fitting portion 42. Then, while the clearance of the third fitting portion 46 is made extremely small, while the clearance of the second fitting portion 44 is made large, the powder 120 is accommodated in the second fitting portion 44, and the third fitting Part 4
There is almost no entry within 6.

After the powder 120 is filled, as shown in FIG. 2, the upper ram is lowered so that the first and second upper punches 86, 92 approach the first and second lower punches 26, 70, and the powder 120 is Compressed. A cushion device is provided between the second upper punch 92 and the upper ram, so that the second upper punch 92 initially has the first upper punch 86.
However, since the cushion device is provided with the stopper, the second upper punch 92 does not retract relative to the first upper punch 86 by a certain amount or more. As the upper punches 86, 92 descend, the first lower punch 26 moves backward against the urging force of the air cylinder 28, and the powder 120 moves downward together with the upper punches 86, 92 while being compressed. And support base 2
When the lower end surface 112 of 7 comes into contact with the contact surface 114 of the block 108, the lowering of the first lower punch 26 is blocked.

The lower ram is also lowered in parallel with the lowering of the first lower punch 26, and the die 80 is lowered by a certain amount via the base plate 10, the guide bar 12 and the die holder 14. Powder 12
With the compression of 0, chamfer 54 on the protrusion 52 of the first lower punch 26.
Side, the pressure acts on the core rod 24 side, and the diameter of the protrusion 52 is reduced.However, in the present embodiment, the clearance of the first fitting portion 42 is large, so that the inside of the first fitting hole portion 34 Of course, the peripheral surface does not directly tighten the core rod 24,
The core rod 24 is also not tightened via the powder 120 that may remain in the first fitting portion 42. Further, since the third fitting portion 46 prevents misalignment between the first lower punch 26 and the core rod 24, the inner peripheral surface of the first fitting hole portion 34 is powdery.
It is also prevented from being strongly pressed against the outer peripheral surface of the core rod 24 via 0. Further, since the second fitting hole portion 36 is provided, the first fitting hole portion 34 and the third fitting hole portion 38 are provided.
Since and are discontinuous, the diameter reduction of the third fitting portion 46 due to the diameter reduction of the first fitting hole portion 34 is reduced. Therefore, although the clearance of the third fitting portion 46 is small, the third fitting hole portion 38 does not tighten the core rod 24,
The lower punch 26 and the core rod 24 slide smoothly in a state where they are accurately positioned in the radial direction, and the occurrence of galling and seizure of the core rod 24 is satisfactorily prevented.

After the compression is completed, the die 80 is lowered and the green compact 122 is extracted from the die 80. Along with that, the cam 104 contacts the cam follower 110 and moves the block 108 to the retracted position. At this time, since the air cylinder 28 applies an upward force to the support base 27, the frictional force between the block 108 and the support base 27 is reduced, and the block 108 is easily moved to the retracted position. Further, since the green compact 122 remains pressed by the upper punches 86, 92, the green compact 122 is pressed by the urging force of the air cylinder 28 via the support base 27 and the first lower punch 26.
It is not suddenly kicked out of.

Next, air is supplied to the second chamber 31 of the air cylinder 28,
As shown in FIG. 3, the first lower punch 26 is lowered to the same height as the upper end surface of the die 80, and is extracted from the green compact 122. Then, the upper punches 86 and 92 are raised. While the first upper punch 86 rises as the upper ram rises, the second upper punch 92 is kept pressed against the green compact 122 by the cushioning action. Therefore, first punch first
86 is extracted from the green compact 122 and then the second upper punch 9
2 will be separated from the green compact 122. Finally,
The green compact 122 is taken out from above the second lower punch 70.

The embodiment of the present invention has been described above. As shown in FIG. 5, the inner diameter of the fitting hole 152 of the lower punch 150 is constant, and the outer diameter of the core rod 154 is different from the cavity side in three steps. Thereby, the first fitting portion 156, the second fitting portion 158, and the third fitting portion 160 can be formed. In this case, the relative movements of the lower punch 150 and the core rod 154 change the axial lengths of the first fitting portion 156 and the third fitting portion 160, but there is no problem.

If the outer diameter of the core rod is made different in two steps and a relief groove with a large inner diameter is formed at the axial center of the fitting hole of the lower punch, or if the inner diameter of the fitting hole of the lower punch is made different in two steps. It is also possible to form the first, second, and third fitting portions by forming the relief groove on the outer peripheral surface of the core rod.

In addition, various modifications and improvements are made based on the knowledge of those skilled in the art, such as applying the present invention to a mold for molding a green compact having a shape different from that of the above embodiment, Can be carried out.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front sectional view showing a green compact molding die according to an embodiment of the present invention. 2 and 3 are front sectional views showing another operating state of the mold. FIG. 4 is a partial front sectional view showing, in an enlarged manner, the fitting portion between the lower punch of the mold and the core rod. FIG. 5 is a partial front sectional view showing another embodiment of the present invention. FIG. 6 is a partial front cross-sectional view showing a state in which the clearance with the core rod is reduced due to the diameter reduction of the lower punch in the conventional die. 24: Core rod, 26: First lower punch 32: Fitting hole, 42: First fitting part 44: Second fitting part, 46: Third fitting part 52: Projection, 80: Die 86: First Upper punch, 100: Cavity 120: Powder, 122: Green compact 150: Lower punch, 152: Fitting hole 154: Core rod, 156: First fitting part 158: Second fitting part, 160: Third fitting Joint section

Claims (1)

(57) [Scope of utility model registration request] 1. A core rod, a lower punch fitted to the outside of the core rod so as to be relatively movable in the axial direction, and arranged outside the lower punch, and relatively movable in the axial direction with respect to the lower punch. A cavity is formed by a plurality of mold members including a die and an upper punch which is provided so as to face the lower punch and can approach and separate from the lower punch, and
In a green compact molding die in which the lower punch has an outer peripheral surface that defines a part of a cavity, a fitting portion between the lower punch and the core rod is provided with a first, a second and a third in order from the cavity side. Divided into mating parts,
A powder compact molding die characterized in that the clearance of the first fitting portion is made larger than that of the third fitting portion and the clearance of the second fitting portion is further increased.