JPH10310803A - Powder compacting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, in powder compacting device in which downward pressing is applied to a die surrounding a rubber mold by an upper punch and the rubber mold is subjected to compressive deformation while the die is descended to compact powder filled in the mold into a prescribed shape, the overhaul of the powder compacting device in whole has been required for the adjustment of pressing force since the die has heretofore been pressed upwardly by a coil spring provided in an outerly inserted state aroung a lower punch. SOLUTION: The surrounding of a lower punch 3 is provided with plural repulsing tools 12 at prescribed intervals. The repulsing tools 12 are ones obtd. by laminating plural coned disc springs while alternating their directions. Thus, by changing the number of the coned disc springs 18 to be used and their directions, the adjustment of the pressing force thereof is made possible. Since the repulsing tools 12 face to the outside, their loading and unloading can relatively easily be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder compacting apparatus used for molding a powder compact such as a magnetic material.

[0002]

2. Description of the Related Art Conventionally, as a powder molding apparatus, a lower punch provided on a die supporting portion, a rubber mold held on the lower punch, and a vertically movable and upwardly movable state surrounding the rubber mold. (See, for example, Japanese Patent Application Laid-Open No. 6-20).
7205 (hereinafter referred to as a first conventional example),
-271705 (hereinafter referred to as a second conventional example) and the like.

In the first prior art, a coil spring is incorporated as a structure for urging the die upward between the upper and lower sides of the die and the die supporting portion so as to fit around the lower punch. Have been. The second conventional example describes that a backup plate harder than the rubber mold is fitted between the upper and lower portions of the lower punch and the rubber mold and between the upper and lower portions of the rubber mold and the upper punch inside the die. This backup plate is for preventing the rubber mold from biting into the gap between the die and the lower punch or the upper punch.

[0004]

SUMMARY OF THE INVENTION In the first conventional example,
When the urging force of the coil spring for urging and holding the die is insufficient, it is expected that the rubber mold will be caught between the upper surface of the die and the upper punch when the upper punch presses down. Therefore, it is necessary to replace the coil spring with one that has a strong biasing force.
This involves disassembling and assembling the die, the lower punch, and the die supporting portion, which is extremely troublesome.

Further, there is a natural limit in selecting a coil spring that can be assembled around the lower punch with a strong urging force, that is, a coil spring having a high spring constant because of its size. Therefore, this type of powder molding apparatus is not suitable for high-pressure molding, for example, exceeding 500 kgf / cm ² .

On the other hand, in such a case, it is conceivable to use the backup plate described in the second conventional example together. In this second conventional example, when the rubber mold is pressed down by the upper punch, the upper punch is used. Since it was necessary to enter the inside of the die as it was, the backup plate also frequently moved inside the die with the movement of the upper punch, and there was a defect that the backup plate was significantly worn.

In addition, this type of powder molding apparatus requires high-precision adjustment in order to insert the upper punch into the die, and is not suitable for practical use in the first place. For this reason, even when the technical elements of the first conventional example and the second conventional example are combined, high-pressure molding cannot be realized. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a powder molding apparatus capable of changing the urging force as a means for urging a die upward, and particularly capable of easily responding to high-pressure molding. A second object is to provide a powder molding apparatus capable of preventing the attachment member from being worn when an attachment member such as a backup plate is used.

[0008]

According to the present invention, the following technical measures have been taken in order to achieve the above object. That is, in the powder molding apparatus according to the present invention, the upper punch is configured to be capable of rolling down not only the die (including the conventional rubber mold) but also the die surrounding the die. Is not inserted inside the die.

As a biasing means for biasing the die upwardly with respect to the die supporting portion, a structure in which a plurality of springs in which a plurality of disc springs are overlapped is arranged upright at a plurality of locations around the lower punch. And The spring device changes the overall spring constant by using a disc spring having a different material, thickness, taper angle, or the like, or by changing the number of disc springs used, the direction in which the disc springs are overlapped, and the like. Things can be done easily. In addition, the use of the disc spring allows the spring constant to be increased without increasing the external size of the spring.

[0010] Therefore, the urging force as the urging means constituted by providing a plurality of the elastic launchers can be easily changed as required. In addition, the above-mentioned spring is provided around the lower punch, that is, between the upper and lower sides of the die and the die supporting portion, so that the spring is provided with the die when replacing or reversing the disc spring. There is no need to disassemble or assemble the lower punch and the die supporting portion.

In this biasing means, when the number of disc springs used in the predetermined arrangement of the springs is reduced or the spring constant is reduced, the individual springs are compressed by the pressure of the upper punch. In other words, it is possible to delicately change and adjust the rolling characteristics, that is, the rolling characteristics in the process of lowering the die, in accordance with various conditions. Therefore, by performing this adjustment, for example, it is possible to cope with a situation in which the density of the raw material powder suddenly changes under a predetermined molding pressure.

On the other hand, the upper punch may be provided with a backup portion which presses between the upper joining portions of the molding die and the die before the molding die is fully reduced. . This backup portion is operatively corresponding to a conventional backup plate, and is for preventing the mold from being caught between the upper surface of the die and the upper punch when the upper punch presses down. It is. Therefore, this backup portion is formed of a material harder than the mold, for example, rubber.

However, in the present invention, the backup portion is already provided in a vertically compressed state when the upper punch presses down the forming die. For example, means for projecting the backup portion downward from the bottom surface of the main body of the upper punch is employed. Therefore, the upper punch and the die are kept in a high contact state at the time of the actual start of the rolling, and there is an advantage that the effect of preventing the mold from biting is improved accordingly.

Since this backup portion does not enter the inside of the die unlike the conventional backup plate, it does not wear inside the die when the upper punch presses down. The backup portion, a material having the same hardness as the material forming the die, for example, formed of metal, between the upper surface joining portion of the mold and the die, a material that is harder than the mold and softer than the backup portion, For example, if an auxiliary backup portion made of rubber is provided, the upper surface of the die and the upper punch come into contact with each other that is hard. However, the auxiliary backup portion surely prevents the molding die from being caught between the upper surface of the die and the upper punch.

Therefore, high pressure molding (for example, 500 kgf /
under a pressure of more than ² cm ² ).

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a powder molding apparatus 1 according to the present invention. The powder molding apparatus 1 includes a lower punch 3 provided on a die supporting portion 2 and a molding die 4 held on the lower punch 3. A die 6 urged upward by the urging means 5 from the die supporting portion 2 in a state surrounding the molding die 4, and an upper punch provided so as to be able to be pressed down with respect to the molding die 4 and the die 6. 7 are provided.

The molding die 4 is made of a material such as rubber which can be vertically compressed and deformed, and its outer shape is formed in a cylindrical shape with a bottom. The internal space opened to the upper surface is formed by
a, the molding recess 4a is a space similar to a desired molded product shape. The die 6 has a cylindrical shape to which the molding die 4 can be fitted, and an intermediate frame 9 for the urging means 5 is coupled to a lower portion thereof. And the die 6
The plurality of guide pins 11 (see FIG. 2) provided between the intermediate frame 9 and the die supporting portion 2 vertically guide the vertical movement and limit the vertical movement stroke.

As shown in FIG. 2, the urging means 5 has a plurality of projecting members 12 which are arranged upright at equal intervals around the lower punch 3. Each projectile 12 is sandwiched between a deep hole 14 formed in the die support 2 and a stepped recess 15 for positioning formed on the lower surface of the intermediate frame 9. As shown in FIG. 3, the spring 12 has a structure in which a plurality of disc springs 18 are superimposed on each other, and a mandrel 19 is inserted in the center thereof in a skewered manner. The lower end of the mandrel 19 is screwed to the bottom of the deep hole 14. In addition, a space of a predetermined height is secured between the upper end of the mandrel 19 and the ceiling surface of the stepped recess 15, and this space allows the downward stroke of the die 6.

Accordingly, the elastic member 12 can be exposed only by removing the guide pin 11 and lifting the die 6, and the elastic member 12 can be attached to and detached from the die supporting portion 2 very easily. I can do it. In the present embodiment, the number of the springs 12 constituting the urging means 5 is six in total, and each of the springs 1
The number of disc springs 18 used in No. 2 was 32, and the direction of superposition was alternately reversed in pairs.

The upper punch 7 has a molding recess 4a of the molding die 4.
And an upper cover 20 for covering the
Ring-shaped backup part 2 surrounding the outer periphery of
1 is provided. The backup portion 21 is formed of rubber, and presses over the upper surface joining portion between the molding die 4 and the die 6 when the upper punch 7 descends as shown in FIG. Backup unit 21
Is formed of a rubber that is harder than the rubber forming the mold 4.

The upper lid 20 and the backup portion 21 are provided so as to project slightly below the bottom surface 7a of the main body of the upper punch 7. Therefore, when the upper punch 7 descends and presses down the molding die 4, at the same time as the upper lid 20 closes the molding concave portion 4 a of the molding die 4, the backup portion 21 makes a gap between the upper surface joining portion of the molding die 4 and the die 6. Pressing is performed.

That is, when the upper punch 7 begins to press down the die 6 and the mold 4 in earnest, the backup unit 2
Since 1 is already in the predetermined vertical compression state, the upper and lower portions of the upper punch 7 and the die 6 are in a close contact state, and the biting of the mold 4 is reliably prevented. Backup unit 21
Is preferably 0.5 mm or more and less than 2 mm, and in this embodiment, 1 mm.

In the powder molding apparatus 1 having such a configuration, after the molding die 4 is filled with a predetermined amount of raw material powder and the upper punch 7 is lowered, the molding recess 4a of the molding die 4 is At the same time as the upper lid 20 is closed, the space between the upper surface joining portions of the molding die 4 and the die 6 is pressed by the backup portion 21, and is maintained in a highly tight state. And upper punch 7
The die 6 is lowered while resisting the urging action of the urging means 5 with the increase in the amount of reduction of the pressing force, and the molding die 4 is vertically compressed while being surrounded by the die 6 and the lower punch 3. The material powder is deformed, and the raw material powder is compression-molded into a predetermined shape in the molding recess 4a of the molding die 4.

FIG. 5 shows a seal portion pressure acting between upper and lower portions of the upper punch 7 and the die 6, a reduction amount by the upper punch 7,
That is, it is a result of examining the limit of breakage of the molding die 4 in relation to the molding pressure. In the graph, a circle indicates that the mold was not damaged, and a cross indicates that the mold was damaged. As is apparent from FIG. 5, when the molding pressure is in the range of approximately 200 to 400 kgf / cm ² , it is understood that the pressure of the seal portion must be maintained at about 1/2 or more of the molding pressure.

Disc spring 1 used for spring 12 of biasing means 5
In FIG. 8, the deflection (deformation amount) and the elasticity (load) can be variously changed by changing the number of sheets used and the direction of superposition as shown in FIG. What is necessary is just to select a use state for appropriately maintaining the relationship between the seal portion pressure and the molding pressure. Of course, it is also possible to replace the disc spring 18 with one having a different material, thickness, taper angle, or the like.

FIG. 7 shows the relationship between the molding pressure and the density of the raw material powder. In the graph, X is Nd-Fe-B, Y is Sr-ferrite, and Y is Sr-ferrite. Z indicates Sm-Co, respectively. As is apparent from FIG. 7, the density of all the raw material powders suddenly changes from 40% to 50% or more when the molding pressure is increased from about 100 kgf / cm ² .

On the other hand, as shown in FIG. 6, in the disc spring 18 used for each of the springs 12 of the urging means 5, the bending (the amount of deformation) and the elasticity (the load) are in a substantially proportional relationship. Therefore, when the molding pressure is set to about 100 kgf / cm ² or less, the disc spring 18 is largely bent due to the low density of the raw material powder (that is, the compression amount is large), and the elasticity is accordingly increased. Therefore, there is a possibility that the seal portion pressure becomes higher than the molding pressure.

Therefore, in this case, when the number of the disc springs 18 used is reduced or the disc springs 18 are replaced with ones having a small spring constant, the upper punch 7 is used. Pressure distribution in which the coned disc spring 18 is compressed by the reduction of
The situation where the density of the raw material powder changes suddenly can be in a similar relationship to each other.

By doing so, 100 kgf / c
Appropriate powder molding can be performed even under a relatively small molding pressure of about m ² or less. In this case, the spring 12
It is also possible to arrange the disc springs 18 acting in the early stage of the compression and the disc springs 18 acting in the later stage, that is, those having different positions in the vertical direction, such that the spring constants are different.

On the other hand, in the case of performing high-pressure molding in which the molding pressure exceeds 500 kgf / cm ² , as described above, the urging means 5 performs an operation such as changing the number of disc springs 18 used or the direction of superposition. However, there is a case where biting of the mold 4 between the upper punch 7 and the die 6 cannot be completely prevented. Therefore, in such a case, FIG.
As shown in (1), the backup portion 21 provided on the upper punch 7 is made of metal, and the auxiliary backup portion 23 is provided on the outer peripheral portion of the upper surface of the molding die 4. The auxiliary backup portion 23 is formed of a material that is harder than the rubber forming the mold 4 and is softer than the backup portion 21, for example, rubber.

By doing so, the contact between the bottom surface 7a of the main body of the upper punch 7 and the die 6 becomes a metal pair, and it can sufficiently withstand high-pressure molding. Incidentally, the present invention is not limited to the above embodiment. For example,
Materials forming the mold 4, the backup portion 21, and the auxiliary backup portion 23 are not particularly limited as long as they satisfy the respective hardness relations.

In the embodiment shown in FIG. 8, a concave portion for fitting the auxiliary backup portion 23 is provided on the outer peripheral portion of the upper surface of the molding die 4, but this concave portion is provided on the inner peripheral portion of the upper surface of the die 6. You may do so.

[0033]

As is apparent from the above description, in the powder molding apparatus according to the present invention, a plurality of springs having a plurality of disc springs are provided around the lower punch as means for urging the die upward. With such a configuration, the biasing force as a whole can be easily changed.

Further, since the upper punch does not enter the inside of the die, the disadvantage that the backup portion is worn relatively early can be solved. Further, by making the backup portion provided on the upper punch a material having the same hardness as the die and providing the auxiliary backup portion on the molding die, it can sufficiently withstand high-pressure molding.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a powder molding apparatus according to the present invention.

FIG. 2 is an enlarged sectional view taken along line AA of FIG.

FIG. 3 is a side cross-sectional view showing a part of a projectile in an enlarged manner.

FIG. 4 is an enlarged side sectional view showing a state in which a molding die is lowered by an upper punch.

FIG. 5 is a graph showing a result of examining a limit of breakage of a molding die in relation to a molding pressure and a seal portion pressure.

FIG. 6 is a graph showing a relationship between deflection and elasticity of a disc spring.

FIG. 7 is a graph showing a relationship between a molding pressure and a density of a raw material powder.

FIG. 8 is a side sectional view illustrating an embodiment in which high-pressure molding is enabled for easy comparison with FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Powder molding apparatus 2 Die support part 3 Lower punch 4 Mold 5 Urging means 6 Die 7 Upper punch 12 Elastic tool 18 Disc spring 21 Backup part 23 Auxiliary backup part

Claims (4)

[Claims] 1. A lower punch (3) provided on a die supporting portion (2), a vertically compressible and deformable forming die (4) held on the lower punch (3), and the forming die (4). ) The die (6), which is urged upward from the die support part (2) by the urging means (5) in a state surrounding the periphery, and can be pressed down to the molding die (4) and the die (6). Upper punch provided (7)
In the powder molding apparatus having the above, the urging means (5) is provided with a plurality of elastic springs (18) stacked on each other at a plurality of positions around the lower punch (3). A powder molding apparatus having a configuration. 2. A molding die (4) is provided on the upper punch (7).
A backup portion (21) for pressing between the upper surface joining portions of the molding die (4) and the die (6) before the rolling of the die;
2. The powder molding apparatus according to claim 1, wherein said backup portion is made of a material harder than the molding die. 3. The back-up portion (21) is formed of a material having the same hardness as the material for forming the die (6), and between the upper surface joining portion of the mold (4) and the die (6). It is harder than the mold (4) and the backup part (2
3. An auxiliary backup portion (23) made of a material softer than (1).
A powder molding apparatus as described in the above. 4. The urging means (5) reduces the number of uses of a disc spring (18) in a predetermined arrangement of a spring (12) or makes the disc spring (18) have a small spring constant. The powder molding apparatus according to any one of claims 1 to 3, wherein: