JP2613529B2 - Method and apparatus for manufacturing powder molded article having undercut portion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a powder molded article having an undercut.

[0002]

2. Description of the Related Art Conventionally, a powder molded product having this kind of undercut portion is manufactured by, for example, an undercut portion 103 between multiple rows of teeth 101 and 102 as shown in FIGS. 8 (a) and 8 (b). 8 (c) to 8 (d).

That is, the powder 107 in the die 106 is pressed by the upper and lower punches 104 and 105 to form a wide sprocket molded body 108, and after sintering, the undercut portion 103 is cut by machining.

[0004]

However, in the above-described conventional manufacturing method, the number of machining steps for shaving the undercut portion 103 increases, which causes an increase in cost. Therefore, it is required to directly form the undercut portion 103 in the powder molding process.

However, when the undercut portion 103 is to be formed by a conventional manufacturing method, as shown in FIG.
03, it was impossible to extract the molded product 109.

On the other hand, Japanese Patent Publication No. 54-41749 (Japanese Patent Application No. 46-73482)
9) includes a die 106 as shown in FIGS. 9 (a) and 9 (b).
A device in which A and 106B are divided in the horizontal direction is disclosed. However, even if molding is performed by this method, as shown in FIG. 9A, the teeth 101 and 102 of the sprocket 100 are caught and cannot be removed.

[0007] The present invention has been made to solve the above-mentioned problems of the prior art.
An object of the present invention is to provide a method and an apparatus for manufacturing a powder molded product having an undercut portion that can directly form an undercut portion by powder molding.

[0008]

According to the present invention, there is provided a method for manufacturing a powder molded article having an undercut portion, comprising the steps of: dividing a die into a plurality of dies; A cam die corresponding to the shape of the undercut portion is provided, the cam die is configured to be able to advance and retreat with respect to the die hole, the powder is filled in the die hole, and the powder is pressed by a punch which is pressed into both ends of the die hole. After the pressurization is completed, the cam die is retracted from the die hole and the molded product is extracted.

[0009] The cam die is divided into a plurality of pieces in the lateral direction.

In the powder filling step, overfilling is performed in which the filling depth is made deeper than a specified position to increase the filling amount.

The punch and the die are moved relative to each other by an amount proportional to the product height from the vertical direction around the cam die,
The relative speed of the punch and die should be such that the compression speed ratio for compressing each part in the entire pressurization process from the start of pressurization to the completion of pressurization is almost the same as the ratio of the compression dimensions of each part of the final molded product It is characterized by controlling a dynamic moving speed.

After the pressurization is completed, the punch is retracted relatively by an appropriate amount around the cam die to reduce or eliminate the force applied to the cam die.

[0013] A sensor is mounted on the cam die, and an error signal is output when there is a difference in pressure from above or below during pressurization and depressurization.

When the product is extruded with the product dispensing rod after the extraction is completed, air is blown out from the dispensing rod and the powder on the dice and the cam die is blown off.

It is characterized in that the powder is sucked from the dispensing rod by vacuum.

An apparatus for manufacturing a powder molded article having an undercut portion, wherein a die having a die hole filled with powder is divided into a plurality of parts with an undercut portion therebetween, and the undercut portion is divided between divided surfaces. A cam die corresponding to the shape is provided, and the cam die is configured to be able to advance and retreat with respect to the die hole.

[0017]

According to the present invention, the undercut portion is extracted by dividing the die into a plurality of parts and, in the extraction step, retracting the cam die from the die hole.

Further, by dividing the cam dies in the horizontal direction, it is possible to form an undercut portion over the entire circumference of the product.

By performing overfilling, it is possible to prevent a shortage of the filling amount due to the cam dies protruding into the die holes.

Further, if the pressure applied to the upper and lower surfaces of the cam die is not increased so as not to cause a difference during the molding, the life of the cam die is affected, and if the difference is large, breakage is caused. Therefore, the pressurizing speed of the punch (the relative speed considering the cam die even when the die moves) is formed at a speed corresponding to the height of the product,
The cam die is formed so that the same force is always applied from above and below.

When the upper punch is lifted and the pressure is released after the pressurization is completed, the residual pressure from the lower punch remains, so that a force is applied to the cam die from below.
As in the case of pressurization, it affects the life of the cam dies and causes product crash. Therefore, after the pressurization is completed, in the withdrawal step, the punch is returned relatively in the direction opposite to the pressurization direction to remove the residual pressure, and in some cases, a slight reverse pressure is applied, and the cam die is retracted to perform the withdrawal. Do.

At this time, a sensor such as a strain gauge is provided on the cam die to detect an occurrence of a difference in force from above and below and output an error signal to stop the pressurization. Failure can be prevented.
It should be noted that a difference in the remaining pressure at the time of extraction is detected in the same manner, and damage to the die can be prevented.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments.

Also in this embodiment, a method of manufacturing a double-row cam sprocket 100 similar to that shown in FIGS. 8A and 8B will be described as an example of a powder molded product having an undercut portion. And

FIGS. 4 and 5 show a schematic configuration of the manufacturing apparatus of the present invention.

This manufacturing apparatus is divided into upper and lower dies 1 and 2 having die holes 1A and 2A filled with powder.
2 and a cam die 3 provided between the divided surfaces of the upper and lower dies 1 and 2 and upper and lower punches 4 and 5 inserted into the upper and lower die holes 1A and 2A. .

The upper punch 4 comprises a cylindrical upper first punch 41 located at the outermost periphery, and a cylindrical upper second punch 42 which is concentrically assembled inside the upper first punch 41. Outside the upper first punch 41, a cylindrical die pressing punch 43 having a lower end in contact with the upper surface of the upper die 1 is provided. The die holding punch 43 and the first and second upper punches 41 and 42 are slidably assembled concentrically with each other.

The lower punch 5 is provided with a lower first punch 51
And a lower second punch 52 on the inside thereof and a core 53 located at the center thereof. The lower first and second punches 51 and 52 and the core 53 are slidably assembled concentrically with each other. ing.

The upper and lower dies 1A and 2A provided in the upper and lower dies 1 and 2 are coaxially arranged with the same diameter, and the upper and lower dies 1 and 2 are located at the centers of the upper and lower dies 1A and 2A. It moves independently in the axial direction.

On the other hand, the cam die 3 is divided into left and right cam die plates 31,32. The divided surfaces of the cam die plates 31 and 32 are the upper and lower die holes 1A and 2
Semicircular cutouts 31A and 32A are formed on the plane including the central axis of A so as to face each other on the divided surfaces of the cam die plates 31 and 32, respectively. Then, by joining the divided surfaces together, a circular undercut-compatible die hole 3A is defined. The undercut-compatible die hole 3A is set to have a smaller diameter than the upper and lower dies 1 and 2 and the upper and lower die holes 1A and 2A, and the circular undercut portion 103 of the double row cam sprocket 100.
Is molded.

In this embodiment, the cam die plate 31,
32 is provided so as to be movable left and right along the upper surface of the lower die 2, and moves up and down together with the lower die 2. Then, the notches 31A, 32A of the left and right cam die plates 31, 32 are provided.
Of the upper and lower dies 1, 2 and the lower die holes 1A, 2
A moves so as to enter and exit the inside and outside of a virtual cylindrical surface connecting the inner peripheral surface of A.

The cam die plates 31, 32
Is provided with a sensor S for detecting a difference between the pressing forces acting on the upper and lower surfaces of the cam die plates 31 and 32. As the sensor S, for example, a strain gauge is used, and a force is detected from a strain amount corresponding to a pressing force. Of course, various force sensors other than the strain gauge can be used.

FIG. 1 and FIG. 2 are flowcharts for forming the above-described cam sprocket.

This operation is of the withdrawal type in which the lower second punch 52 is fixed. Of course, the lower die 2 may be fixed, and the upper and lower punches 4 and 5 may be used in a double-pressing method in which pressure is applied from above and below.

FIG. 1A shows a state in which the powder 7 is put in the die holes 1A, 2A, 3A of the dies 1, 2 and the cam die 3 above and below the feeder 6. Just by filling,
Since a portion 7A in which powder does not enter is formed below the hole edge of the undercut corresponding die hole 3A of the cam die 3, the upper die 1, the cam die 3, and the lower die 2 are raised from the specified positions by that amount to increase the filling depth. The filling amount is increased by the amount that the powder does not enter to bring the overfill state.

It is also effective to apply vibration to the lower first punch 51.

Then, although not shown, the feeder 6, the upper die 1, the cam die 3, and the lower die 2 are simultaneously lowered to make the powder 7 uniformly filled.

Thereafter, the feeder 6 retreats, the upper first and second upper punches 41 and 42 and the die pressing punch 43 descend, and the filling state shown in FIG.

In FIG. 1 (c), the filling powder is transferred to make the filling depth proportional to the height of the product.

That is, with the lower first punch 51 fixed, the upper first and upper second punches 41 and 42, the die holding punch 43, the upper die 1, the cam die 3, the lower die 2, and the lower first punch 51 are removed. At the same time, the prescribed amount is lowered to make the filling amount proportional to the product height as shown in FIG.

In the cam sprocket of this embodiment, FIG.
As shown in FIG. 5, the pressed portion includes a first pressing portion A between the upper surface of the cam die 3 and the upper first punch 41, a second pressing portion B between the lower surface of the cam die 3 and the lower first punch 51, Third pressing portion C between upper second punch 42 and virtual neutral surface N of cam die 3
And a fourth pressing portion D between the lower second punch 52 and the virtual neutral surface N of the cam die 3. The product height of each pressurizing section after the pressurization is completed is a1, b1, c1, d1.
Assuming that the filling depth is a0, b0, c0, d0, the ratio between the filling depth and the product height of each part is set to be the same. Usually, the filling depth of each part is set to about twice the product height.

In FIG. 1D, pressure is applied by proportional molding.

However, in this case, it is necessary to form the cam die 3 so that a neutral zone is formed around the cam die 3 so as not to cause a difference in the pressing force from above or below. That is, at any time during the pressing, the dimensions of the first, second, third, and fourth pressing parts A, B, C, and D are controlled so as to maintain the same ratio as the ratio of the products. is there. In other words, the punch and the die are relatively moved by an amount proportional to the product height from the vertical direction about the cam die 3,
The pressurizing speed ratio for compressing each part in the entire pressurizing process from the start of pressurization to the completion of pressurization is determined by the dimensions a0,
so that the ratios of b0, c0 and d0 are almost the same.
Upper and lower dies 1 and 2 and cam die 3
The relative movement speed between the second punches 41 and 42 and the lower first punch 51 is controlled.

During the pressurization, the sensor S detects the difference in the forces acting on the upper and lower sides of the cam die plates 31 and 32, and if the difference in the forces becomes excessive, an error signal is output and the pressurization is stopped. The breakage of the cam die 3 can be prevented.

The upper die 1 is thin because the height is determined by the thickness a0 of the product. When the upper die 1 is in close contact with the cam die 3 by hydraulic pressure from both sides, a large force cannot be generated. It is better to press the upper die 1.

FIG. 1 (d) shows the completion of pressurization. As shown in FIG. 3 (a), after pressurization, the upper and lower punches 4 and 5 retreat or relatively retreat (when the lower second punch 52 is fixed). The same applies if the amount of rise of each punch and die is specified), and the die holding punch 43 and the upper die 1 are raised with a certain amount of residual pressure left to be in the state shown in FIG. 3B (to prevent cracks). .

In FIG. 3C, the lower die 2 and the lower first punch 5
1 and the core 53 are lowered, and the extraction of FIG. 3C is completed. Immediately thereafter, as shown in FIG.
Moves forward, pushes the product 9 forward, and blows out air from the hole 8A at the tip of the product delivery rod 8 to remove the powder adhering to the cam die 3, the lower die 2, the lower first and second punches 51, 52. Blow it away. In some cases, the water may be sucked up by vacuum.

Then, the product payout rod 8 returns, the cam die 3 moves forward, the upper die descends and comes into close contact with the cam die 3, and then the upper die 1, the cam die 3, the lower die 2, the lower first punch 51 and the core 53. Rises to the prescribed position,
The feeder 6 advances again and returns to the filling step shown in FIG.

FIG. 6 shows the overall conceptual configuration of the above-described apparatus. That is, the die holding punch 43, the upper first
The second punches 41 and 42 are respectively provided with a die pressing punch driving mechanism 203 and upper first and second punch driving mechanisms 201 and 20.
2, the lower first and second punches 51 and 52, and the core 53 are driven vertically by the first and second lower punch driving mechanisms 203 and 204 and the core driving mechanism 205.

The upper and lower dies 1 and 2 are driven up and down by upper and lower die driving mechanisms 206 and 207, and the cam die 3 is driven by the cam dice driving mechanism 208 in the right and left direction.

Further, these die press driving mechanisms 203,
First and second upper punch driving mechanisms 201 and 202, first and second lower punch driving mechanisms 204 and 205, core driving mechanism 20
6, the upper and lower die driving mechanisms 207 and 208 and the cam die driving mechanism 209 are connected to the drive control means 210, and the driving procedure of each unit is controlled.

As each drive mechanism, various drive mechanisms such as a hydraulic cylinder such as a hydraulic pressure, a screw drive mechanism such as a ball screw, and a crank mechanism can be employed. In the above-described embodiment, a double-row cam sprocket has been described as an example of a powder molded product having an undercut portion. However, the present invention is not limited to this, and has an undercut portion 11 as shown in FIG. The molded article 10 can also be manufactured, and various other molded articles can be manufactured.

[0053]

According to the present invention, the undercut portion can be formed in the step of powder molding since the undercut portion can be formed in the powder forming process. Can be reduced.

By performing overfilling, it is possible to prevent a shortage of the filling amount due to the cam dies projecting into the die holes.

The pressing speed of the punch (the relative speed with respect to the cam die even when the die moves) is formed at a speed corresponding to the height of the product, and the same force is always applied to the cam die from above and below. By forming such that it is added, the life of the cam die can be extended and breakage can be prevented.

Further, after the pressurization is completed, in a removal step, the punch is returned relatively in the direction opposite to the pressurization direction to remove the residual pressure, and in some cases, a slight reverse pressure is applied to retract the cam die. By performing the pull-out, not only the life of the cam die can be extended, but also the product can be prevented from crashing.

Further, by detecting that a difference is generated between the forces acting on the upper and lower sides of the cam die and outputting an error signal, the die can be prevented from being damaged.

[Brief description of the drawings]

FIGS. 1 (a) to 1 (e) are process diagrams up to the pressing step in the method for producing a powder molded product having an undercut according to the present invention.

FIG. 2 is a schematic diagram of a die for explaining a proportional pressurizing step in FIG. 1;

FIGS. 3 (a) to 3 (e) are process diagrams up to a product extracting step of the method for producing a powder molded product having an undercut according to the present invention.

FIG. 4 is a sectional view showing a schematic configuration of an apparatus for producing a powder molded product having an undercut according to the present invention.

FIG. 5 is an exploded perspective view of the device of FIG. 4;

FIG. 6 is a block diagram schematically illustrating an example of the overall configuration of the apparatus in FIG. 4;

7 (a) to 7 (c) are a front view, a side view and a plan view of a molded article having another undercut to which the present invention is applied.

8 (a) to 8 (f) are explanatory diagrams for explaining a conventional method for producing a powder molded product having an undercut portion.

FIG. 9 shows an apparatus for explaining another conventional method for producing a powder molded product having an undercut portion. FIG. 9 (a) is a plan view, and FIG. 9 (b) is a cross-sectional view. It is.

[Explanation of symbols]

 Reference Signs List 1 upper die 1A upper die hole 2 lower die 2A lower die hole 3 cam die 3A die hole corresponding to undercut 31, 32 cam die plate 4 upper punch 41 upper first punch 42 upper second punch 43 die holding punch 5 lower punch 51 lower First punch 52 Lower second punch 53 Core 6 Feeder 7 Powder A, B, C, D First, Second, Third, Fourth pressing part

Claims (9)

(57) [Claims] 1. A method for producing a powder molded product having an undercut portion, comprising: dividing a die into a plurality of portions; providing a cam die corresponding to the shape of the undercut portion between divided surfaces; The die hole is filled with powder, the powder is pressurized by a punch press-fitted from both ends of the die hole, and after the pressurization is completed, the cam die is retracted from the die hole to form a molded product. A method for producing a powder molded article having an undercut portion, wherein the molded article is extracted. 2. The method for producing a powder molded product having an undercut according to claim 1, wherein the cam die is divided into a plurality of pieces in the lateral direction. 3. The method for producing a powder molded article having an undercut portion according to claim 1, wherein in the powder filling step, a filling depth is made deeper than a predetermined position to perform an overfill to increase a filling amount. 4. A pressing speed at which the punch and the die are moved relative to each other by an amount proportional to the product height from the vertical direction about the cam die, and each part is compressed in the entire pressing process from the start of pressing to the completion of pressing. 4. The relative movement speed of the punch and the die is controlled so that the ratio is substantially the same as the ratio of the compression size of each part of the final molded product. A method for producing a powder molded product having an undercut portion. 5. The method according to claim 1, wherein after the pressurization is completed, the punch is retracted relative to the cam die by an appropriate amount to reduce or eliminate the force applied to the cam die. A method for producing a powder molded product having an undercut portion. 6. An error signal is output when a sensor is attached to a cam die and a difference occurs in pressure from above or below during pressurization and depressurization.
6. A method for producing a powder molded product having an undercut portion according to 3, 4, or 5. 7. When the product is pushed out with the product payout rod after the extraction is completed, air is blown out from the payout rod,
7. The method for producing a powder molded article having an undercut according to claim 1, wherein the powder on the die and the cam die is blown off. 8. The method for producing a powder molded article having an undercut according to claim 1, wherein the powder is sucked from the payout rod by vacuum. 9. An apparatus for producing a powder molded product having an undercut portion, wherein a die having a die hole filled with powder is divided into a plurality of parts with an undercut portion therebetween, and an undercut is provided between divided surfaces. An apparatus for manufacturing a powder molded product, comprising: a cam die corresponding to a shape of a part;