JPH01119604A - Powder molding method - Google Patents

Abstract

PURPOSE:To form a powder molding having a uniform density by partly moving lower punches to mold the powder packed in a die to the shape which resembles to the shape of the molding, then varying the spacings between the respective pressing faces of the inside and outside punches of an upper punch and the powder and pressurizing and compressing the powder. CONSTITUTION:The die 17 is provided to the outside circumference of the plural lower punches 14, 15, 16 disposed to an annular shape and a core rod 18 is provided to the inside circumference thereof. The powder is packed into the packing part A formed in such a manner. The lower punch consisting of the inside punch and the outside punch 20 formed with a slope 21 is then lowered and is stopped in such a manner that the inside punch 19 parts at a specified spacing from the powder surface when the outside punch 20 comes into contact with the surface of the powder. The lower punches 14, 15 facing the outside punch 20 is then lowered to transfer part of the powder and to form the packed part A to the shape which resembles approximately to the molding shape. The powder is then pressurized and compressed from above and below by the respective punches 14, 15, 16, 19, 20. The movement of the outside punch 20 is thereby surely executed and the powder molding having good quality is obtd.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention involves transferring powder filled in a mold so that it has a shape almost similar to the shape of a molded product by moving a part of a punch, and then This invention relates to improvements in powder compaction methods for forming powder compacts by compressing powder.

(Prior Art) Conventionally, as a method of pressurizing and compressing metal powder etc. to form a powder compact, there is a method described in "Mechanical Design" Volume 30, No. 1O (1
As described in the September issue of 1986, pages 33-34), the powder filling part is formed by using a plurality of layers arranged above and below so that the powder filling part has a shape almost similar to the shape of the powder compact to be molded. After the punches are moved, the powder in the filling part is generally compressed and molded by each punch.

By the way, as shown in FIG. 4, a powder compact 3 having a shape consisting of an annular main body l and a boss part 2 provided on one side of the main body l and having a draft angle S formed on the outer periphery is formed. In this case, if the powder filling part is defined in advance using an upper punch and a lower punch to have a similar shape to the powder compact, the inside of the filling part will be bent, making it impossible to uniformly fill the powder.

Therefore, the filling part is made into a shape that is easy to fill with powder, and after filling the powder in that shape, a part of the punch is moved to define the filling part in a shape that is almost similar to the powder compact to be molded. Compression molding is performed (such a powder molding method is disclosed, for example, in Japanese Patent Application No. 120578/1983). Note that as the punch moves at this time, some of the powder is transferred.

As an apparatus for performing molding in this way, for example, the fifth
There was something like the one shown in the figure.

The lower die (not shown) includes a die 5 held by a die holder 4 and a plurality of lower punches 6, 7 arranged in an annular manner.
．． 8 and a centrally located core rod 9. Each of the lower punches 6, 7, and 8 is connected to a hydraulic cylinder (not shown) at its lower end, so that it can move up and down.

The upper mold (not shown) has an annular inner puncher and outer punch 1.
A hydraulic cylinder (not shown) is connected to the upper end of the outer punch 11, and the outer punch 11 is movable up and down.

Further, a slope 13 for forming a draft angle S of the boss portion 2 of the powder molded product is formed on the surface (inner peripheral surface) of the outer punch 11 that slides with the inner punch 10.

According to this configuration, as shown in FIG. 10 and the outer punch 11 are lowered. After the inner punch 10 and the outer punch 11 are brought into contact with the surface of the powder at the same time, the outer punch 11 and the lower punch 6.7 facing the outer punch 11 are pressed as shown in FIG. The filling part A is made to have a shape substantially similar to the powder molded product 3 by lowering the powder and transferring the powder.

Subsequently, the powder is compressed under pressure using punches 6.7, 8.degree. 10 and 11 to form a powder compact 3.

(Problem to be solved by the invention) However, when molding the powder compact 3 as shown in FIG. 13 is formed, and when the inner puncher and the outer punch 11 come into contact with the powder, the powder enters the gap created by the slope 13.
Then, the powder that has entered acts like a wedge and prevents the outer punch 11 from descending.

Therefore, the relative movement between the outer punch 11 and the inner punch 10 and the powder transfer are not sufficient, and the density of the filled powder becomes uneven, resulting in quality defects such as cracks in the powder molded product 3. There was a problem that occurred.

The present invention has been made in view of one or more problems, and its purpose is to mold a powder compact of good quality by ensuring relative movement between an inner punch and an outer punch. It is in.

(Means for Solving the Problems) A powder compaction method for solving the above problems will be explained based on FIGS. 1 to 3.

Powder is filled into a filling part A formed by a plurality of lower punches 14, 15.16 arranged in an annular manner, a die 17 located on the outer periphery of the lower punches 14, 15.16, and a core rod 18 located on the inner periphery. , from above the filling part A, an inner punch 19, and an outer punch 20 that is in sliding contact with the outer periphery of the inner punch 19 and has a slope 21 formed on the sliding surface for forming a draft angle S of the molded product. lower.

Subsequently, when the outer punch 20 comes into contact with the surface of the powder, the inner punch 19 is stopped at a certain distance from the surface of the powder.

Then, the outer punch 20 and the lower punch 14.15 facing the outer punch 20 are lowered to transfer a part of the powder so that the filling part A has a shape almost similar to the shape of the molded product, and then The powder is compressed from above and below using the punches 14, 15, 16, 19, and 20 to form a powder compact.

(Function) In this way, when the outer punch 20 comes into contact with the powder surface of the filling part A, by keeping the inner punch 19 a certain distance away from the powder surface, the slope 21 formed on the outer punch 20 Powder will not enter the gap that is created, and the relative movement between the outer punch 20 and the inner punch 19 will not be hindered.

Therefore, the powder will be transferred reliably.

(Example) Next, an example of the present invention will be described based on FIGS. 1 to 4.

First, the configuration will be explained using FIG. 1. Three lower punches 14, 15, 16 are arranged slidably in an annular shape in a lower die (not shown), and each of the lower punches 14, 15
．． A hydraulic cylinder (not shown) is connected to the lower end of 16, so that it is movable up and down.

Further, a die 17 is in sliding contact with the outside of the lower punch 14, and a core loft 18 is in sliding contact with the inside of the lower punch 16. And lower punch 14, 15° 16, die 1
7. The core rod 18 forms a filling part A filled with powder.

On the other hand, the upper die (not shown) is provided with an annular inner punch 19 and an outer punch 20 in a slidable manner.
A hydraulic cylinder (not shown) is connected to the upper end of the holder so that it can be moved up and down. Further, an inclined surface 21 forming a draft angle S of the powder compact 3 is formed on the inner circumferential surface of the outer punch 20 in sliding contact with the inner punch 19 .

Further, the inner punch 19 is fixed to an upper die jig 22 that is provided on an upper die (not shown) so as to be slidable in the vertical direction. A coil spring 23 is interposed in the inner punch 19, and the upper end of the coil spring 23 is fixed to a jig 24 with a bolt (not shown) or the like, and the jig 24 is attached to the inside with a bolt 25. It is fixed to the punch 19 and the upper die jig 22. The coil spring 23 is arranged so that when the outer punch 20 comes into contact with the powder filled in the filling part A, a certain gap (about 2×1) is created between the inner punch 19 and the powder surface. It is set to generate elastic force sufficient to lift the inner punch 19 and the upper die jig 22.

A method of using the apparatus having the above configuration will be explained with reference to FIGS. 1 to 3.

First, the lower punches 14, 15, and 16 are appropriately arranged to form a filling part A so that powder can be easily filled (see FIG. 1).

Subsequently, once the filling portion A is filled with powder, the upper die is lowered, and the inner punch 19 and outer punch 20 are lowered. When the outer punch 20 comes into contact with the powder surface, the inner punch 19 is lifted by the elastic force of the coil spring 23 and stopped at a constant height from the powder surface (see FIG. 2).

Next, by lowering the outer punch 20 using a hydraulic cylinder (not shown) and lowering the lower punches I4 and 15 facing the outer punch 20 at the same time, the powder between the outer punch 20 and the lower punches 14 and 15 is removed. Transferred to filling section A
is made into a shape almost similar to the powder compact 3 to be molded (see FIG. 3).

If the upper mold continues to descend in this state, each punch 14
, 15, 16. l! 1.20 is backed up in the upper and lower molds to compress the powder.

In this way, when the outer punch 20 comes into contact with the powder surface, the inner punch 19 is lifted a certain distance from the powder surface to prevent contact, so that the powder does not enter into the gap created by the slope Z1 forming the draft angle. , the relative movement of the outer punch 20 is not hindered. Therefore,
The powder can be transferred reliably, and a powder compact of good quality and uniform density can be obtained.

(Effects of the Invention) As explained in detail above, in the present invention, by keeping the inner punch away from the powder surface during molding, the powder does not enter into the gap created by the slope forming the draft of the outer punch. Therefore, the movement of the outside punch can be performed reliably,
Powder transfer failures will no longer occur.

Therefore, pressure compression can be performed in a state where the density of the powder is uniform, and a powder compact of good quality can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an example of the apparatus used in the powder compacting method of the present invention, and is a longitudinal sectional view showing the state before compaction. FIG. 2 is a longitudinal sectional view of the apparatus shown in FIG. Fig. 3 is a vertical cross-sectional view showing the state when the outer punch descends and transfers the powder in the device shown in Fig. 1; Fig. 4 shows one punch. FIG. 5 is a vertical cross-sectional view showing an example of a powder compact to be molded by the powder molding method of the invention, and FIG. FIG. 6 is a longitudinal cross-sectional view showing the apparatus shown in FIG. 5 when powder is transferred by the outer punch. Note that FIGS. 2, 3, 5, and 6 show only left side cross sections because they are symmetrical. 14.15.16...Lower punch 17...Dice 18...Core lot 19...Inner punch 20...Outer punch 21...Wound surface A...Filling part Patent applicant Toyota Motor Corporation Figure 1 below Iguo Figure 2! Figure 3

Claims (1)

[Claims] (1) A filling part formed by a plurality of lower punches arranged in a ring, a die located on the outer periphery of the lower punch, and a core rod located on the inner periphery is filled with powder, and the inner punch is filled from above the filling part. and an outer punch which is in sliding contact with the outer periphery of the inner punch and whose sliding surface has a slope for forming a draft on the molded product, is simultaneously lowered, and the outer punch is brought into contact with the surface of the powder. When this happens, the inner punch is stopped at a certain distance from the surface of the powder, and then the outer punch and the lower punch facing the outer punch are lowered to form a shape that is almost similar to the shape of the molded product. A powder compacting method characterized in that after transferring a part of the powder so as to have the following properties, the powder is pressurized and compressed from above and below using each of the punches to form a powder compact.