JPH0639596A - Method and apparatus for manufacturing powder molded product having undercut portion - Google Patents

Abstract

PURPOSE:To enable the direct molding of undercut parts in powder molding by dividing dies to a plurality providing cam dies corresponding to the shapes of the undercut part between parting planes and constituting the cam dies in such a manner that the dies can advance and retreat to and from die holes. CONSTITUTION:Powder 7 is put into the die holes 1A, 2A, 3A of the upper and lower dies 1, 2 and the cam dies 3 from a feeder 6 and the amt. of packing is increased more than the regulated amt. to make an overfeed state. The feeder 6 is thereafter retrated and the upper fist and upper second punches 41, 42 and a pressing punch 43 are lowered to form the packed state. The transfer of the packed powder is executed in order to attain the packing depth proportional to the height of the products and the pressurization is executed by proportional molding. The upper and lower punches 4, 5 are retreated or relatively retreated upon completion of the pressurization and the die pressing punch 43 and the upper die 1 are risen by allowing the residual pressure to remain to some extent. The lower die 2 as well as the lower first punch 51 and the core 53 are lowered to complete withdrawal. The products are ejected by product ejector rods 8 right thereafter.

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 product having an undercut portion.

[0002]

2. Description of the Related Art Conventionally, a powder molded product having an undercut portion of this kind has been manufactured by forming an undercut portion 103 between a plurality of rows of teeth 101 and 102 as shown in FIGS. 8 (a) and 8 (b). An example of the sprocket 100 having is described. The sprocket 100 is molded as shown in FIGS. 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 compact 108, and after sintering, the undercut portion 103 is cut by machining.

[0004]

However, in the above-mentioned conventional manufacturing method, the number of machining steps for cutting out the undercut portion 103 increases, which causes a cost increase. Therefore, it is required to directly form the undercut portion 103 in the powder forming process.

However, when it is attempted to form the undercut portion 103 by the conventional manufacturing method, as shown in FIG. 8 (f), a part of the die 106 is the undercut portion 1 of the molded product.
It was not possible to pull out the molded product 109 in order to get into 03.

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

The present invention has been made in order to solve the above-mentioned problems of the prior art, and its purpose is to:
An object of the present invention is to provide a manufacturing method and a manufacturing apparatus of a powder molded product having an undercut portion that can be directly molded by powder molding.

[0008]

In order to achieve the above object, in the present invention, there is provided a method for producing a powder molded article having an undercut portion, which comprises dividing a die into a plurality of divided surfaces. A cam die corresponding to the shape of the undercut portion is provided, the cam die is configured to be capable of advancing and retreating with respect to the die hole, the die hole is filled with powder, and the powder is pressed by a punch press-fitted from both end opening portions of the die hole. It is characterized in that after the pressurization is completed, the cam die is retracted from the die hole to withdraw the molded product.

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

In the powder filling step, the filling depth is made deeper than the specified position to perform the overfilling to increase the filling amount.

The punch and the die are moved relative to each other by an amount proportional to the product height in the vertical direction centering on the cam die,
The relative speed of punches and dies should be adjusted so that the ratio of compression speed at which each part is compressed 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 dimension of each part of the final molded product. It is characterized in that the moving speed is controlled as desired.

After the pressurization is finished, the punch is moved back relative to the cam die by an appropriate amount to reduce or eliminate the force applied to the cam die.

It is characterized in that a sensor is attached to the cam die and an error signal is output when a pressure difference from above or below is generated at the time of pressurization and depressurization.

After the extraction is completed, when the product is extruded by the product expulsion rod, air is expelled from the expulsion rod, and the powder on the die and the cam die is blown off.

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

A manufacturing apparatus for 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 the undercut portion is divided between divided surfaces. It is characterized in that a cam die corresponding to the shape is provided and the cam die can be moved forward and backward 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 pieces and retracting the cam die from the die hole in the extracting step.

By dividing the cam die in the lateral direction, it is possible to form the undercut portion over the entire circumference of the product.

By performing overfilling, it is possible to prevent the filling amount from being insufficient due to the cam die protruding into the die hole.

Further, if the pressurizing force acting on the upper surface and the lower surface of the cam die does not become different during the molding, the life of the cam die is affected, and if the difference becomes large, it will be damaged. Therefore, the punch pressing speed (relative speed with the cam die at the center even when the die moves) is molded at a speed according to the height of the product,
Mold so that the same force is always applied to the cam die from above and below.

Further, when the upper punch is lifted and depressurized at the time of withdrawal after the completion of pressurization, the residual pressure due to the lower punch remains, so that force is applied from below to the cam die,
Like the pressurization, it affects the life of the cam die and causes the product to crash. Therefore, after the pressurization is completed, in the extraction process, the punch is relatively returned in the direction opposite to the pressurizing direction to remove the residual pressure, and in some cases, a little reverse pressure is applied to retract the cam die and extract it. To do.

At this time, if a sensor such as a strain gauge is provided on the cam die, an error signal is output by detecting that a difference between the upper and lower forces is generated, and the pressurization is stopped, damage to the die or the like occurs. It is possible to prevent problems.
It should be noted that even if there is a difference in residual pressure at the time of withdrawal, it can be similarly sensed and damage to the die can be prevented.

[0023]

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

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

4 and 5 show the schematic construction of the manufacturing apparatus of the present invention.

This manufacturing apparatus is provided with die holes 1A and 2A filled with powder, and is divided into upper and lower dies 1 and 2.
2, 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 is composed of a cylindrical upper first punch 41 located on the outermost periphery and a cylindrical upper second punch 42 which is concentrically assembled inside the upper first punch 41. On the outside of the upper first punch 41, a cylindrical die pressing punch 43 whose lower end abuts on the upper surface of the upper die 1 is provided. The die pressing punch 43 and the upper first and second punches 41 and 42 are concentrically slidably assembled to each other.

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

The upper and lower die holes 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 die holes 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 and 32. The split surfaces of the cam die plates 31 and 32 are the above-mentioned upper and lower die holes 1A and 2
The semicircular cutouts 31A and 32A are formed on the divided surfaces of the cam die plates 31 and 32, respectively, which are located on the plane including the central axis of A and face each other. By joining the divided surfaces, 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 lower die holes 1A and 2A, and the circular undercut portion 103 of the double-row cam sprocket 100.
To mold.

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 cutouts 31A, 32A of the left and right cam die plates 31, 32
Edges of the upper and lower dies 1, 2, upper and lower die holes 1A, 2
It moves so as to move in and out of the virtual cylindrical surface connecting the inner peripheral surface of A.

Further, the cam die plates 31, 32
Is provided with a sensor S that detects a difference in pressure applied to 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 the force is detected from the strain amount according to the applied pressure. Of course, various force sensors other than the strain gauge can be used.

1 and 2 are molding sequence diagrams of the above-mentioned cam sprocket.

This operation is a withdrawal method 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 pressed from above and below in a double-pressing method. Alternatively, another die or one of the punches may be fixed to perform molding.

FIG. 1A shows a state in which the powder 7 is put in the die holes 1A, 2A, 3A of the upper and lower dies 1, 2 and the cam die 3 above the feeder 6. Just by filling,
Since there is a portion 7A in which powder does not enter below the hole edge of the undercut-compatible die hole 3A of the cam die 3, the upper die 1, the cam die 3, and the lower die 2 are raised by a corresponding amount to deepen the filling depth. , The filling amount is increased as much as the powder does not enter, and the state is overfilled.

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

Although not shown, the feeder 6, the upper die 1, the cam die 3, and the lower die 2 are simultaneously lowered so that the powder 7 is uniformly filled.

After that, the feeder 6 retracts, the upper first and second punches 41 and 42 and the die pressing punch 43 descend, and the filling state shown in FIG. 1B is obtained.

In FIG. 1 (c), the filling powder is transferred in order 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 pressing punch 43, the upper die 1, the cam die 3, the lower die 2 and the lower first punch 51 are arranged. At the same time, the specified amount is lowered to make the filling amount proportional to the product height as shown in Fig. 1 (c).

In the cam sprocket of this embodiment, as shown in FIG.
As shown in FIG. 3, the portion to be pressed is 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, The third pressing portion C between the upper second punch 42 and the virtual neutral surface N of the 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. Then, the product heights after completion of pressurization of the respective pressurizing parts are a1, b1, c1, and 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. 1 (d), pressure is applied by proportional molding.

However, in that case, it is necessary to form the neutral point centering on the cam die 3 so as not to make a difference in the pressure applied to the cam die from above or below. That is, the dimensions of the first, second, third and fourth pressurizing parts A, B, C, D are controlled so as to maintain the same ratio as the product ratio at any time during pressurization. is there. In other words, the punch and the die are moved relative to each other about the cam die 3 in the vertical direction by an amount proportional to the product height,
The pressurizing speed ratio for compressing each part in the entire pressurizing process from the start of pressurization to the completion of pressurization is the dimension a0 of each part of the final molded product,
so that the ratio is almost the same as the ratio of b0, c0, d0,
Upper and lower dies 1, 2 and cam die 3 and upper first 1,
The relative moving speed between the second punches 41 and 42 and the lower first punch 51 is controlled.

During this pressurization, the sensor S detects the difference between the forces acting on the upper and lower sides of the cam die plates 31 and 32, and when the difference between the forces becomes excessive, an error signal is output and the pressurization is stopped. It is possible to prevent damage to the cam die 3.

The upper die 1 is thin because its height is determined by the product thickness a0, and when it comes into close contact with the cam die 3 by hydraulic pressure from both sides, a large force cannot be produced. It is even better to press the upper die 1.

FIG. 1 (d) shows that the pressurization is completed. After pressurizing, the upper and lower punches 4 and 5 retreat or relatively retreat (when the lower second punch 52 is fixed, as shown in FIG. 3 (a). This is the same if the amount of rise of each punch and die is specified.) With some residual pressure left, the die pressing punch 43 and the upper die 1 are raised to the state shown in FIG. 3 (b) (for crack prevention). .

In FIG. 3C, the lower die 2 and the lower first punch 5 are
1 and the core 53 are lowered to complete the extraction as shown in FIG. 3 (c). Immediately after that, as shown in FIG. 3 (d), the product dispensing rod 8
Moves forward, pushes out 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. You should blow it away. Moreover, you may suck up by vacuum depending on the case.

Then, the product dispensing bar 8 returns, the cam die 3 advances, 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 specified 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-mentioned apparatus. That is, the die pressing punch 43, the upper first,
The second punches 41 and 42 include a die pressing punch driving mechanism 203, upper first and second punch driving mechanisms 201 and 20, respectively.
2, the lower first and second punches 51 and 52 and the core 53 are further driven vertically by the first and second lower punch drive mechanisms 203 and 204 and the core drive mechanism 205.

The upper and lower dies 1 and 2 are driven vertically by the upper and lower die driving mechanisms 206 and 207, and the cam die 3 is laterally driven by the cam die driving mechanism 208.

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

As each drive mechanism, various drive mechanisms such as a hydraulic cylinder for hydraulic pressure, a screw drive mechanism for a ball screw, a crank mechanism and the like can be adopted. In the above embodiment, the double-row cam sprocket is described as an example of the powder molded product having the undercut portion, but the invention is not limited to this, and for example, the undercut portion 11 as shown in FIG. 7 is provided. The molded product 10 can also be manufactured, and various other molded products can be manufactured.

[0053]

EFFECTS OF THE INVENTION The present invention has the above-described structure and operation. Since the undercut portion can be formed in the step of powder molding, it does not require machining as in the conventional case, and the manpower required for processing is reduced. Can be reduced.

By performing overfilling, it is possible to prevent the filling amount from being insufficient due to the cam die protruding into the die hole.

Further, the punching speed (relative speed around the cam die even when the die moves) is formed at a speed according to the height of the product, and the same force is always applied to the cam die from above and below. By forming the cam die so as to be added, the life of the cam die can be extended and the damage can be prevented.

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

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

[Brief description of drawings]

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

FIG. 2 is a schematic diagram of a die for explaining the proportional pressurizing step of FIG.

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

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

FIG. 6 is a block diagram schematically showing an example of the overall configuration of the apparatus shown in FIG.

7A to 7C are a front view, a side view and a plan view of a molded product having another undercut portion to which the present invention is applied.

8A to 8F are explanatory views for explaining a conventional method for manufacturing a powder molded product having an undercut portion.

9A and 9B show an apparatus for explaining another conventional method for manufacturing a powder molded product having an undercut portion, wherein FIG. 9A is a plan view and FIG. 9B is a sectional view. Is.

[Explanation of symbols]

 1 Upper die 1A Upper die hole 2 Lower die 2A Lower die hole 3 Cam die 3A Undercut compatible die hole 31,32 Cam die plate 4 Upper punch 41 Upper first punch 42 Upper second punch 43 Die pressing punch 5 Lower punch 51 Lower 1st punch 52 Lower 2nd punch 53 Core 6 Feeder 7 Powder A, B, C, D 1st, 2nd, 3rd, 4th pressurization part

Claims (9)

[Claims] 1. A method of manufacturing a powder molded article having an undercut portion, wherein a die is divided into a plurality of pieces, and a cam die corresponding to the shape of the undercut portion is provided between divided surfaces, and the cam die is inserted into a die hole. The die hole is filled with powder, and the powder is pressed by punches press-fitted from the openings at 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, which is characterized by extracting. 2. The method for producing a powder molded product having an undercut portion 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, the filling depth is deeper than the specified position to perform overfilling to increase the filling amount. 4. A pressurizing speed for relatively moving the punch and the die by an amount proportional to the product height in the vertical direction around the cam die and compressing each part in the entire pressurizing process from the start of pressurization to the completion of pressurization. 4. The relative moving speed of the punch and the die is controlled so that the ratio becomes substantially the same as the ratio of the compression dimension 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, 2, 3 or 4, wherein after the pressurization is completed, the punch is retreated 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. A cam die is provided with a sensor to output an error signal when a pressure difference from above or below is generated during pressurization and pressure release.
A method for producing a powder molded article having an undercut portion according to 3, 4, or 5. 7. After the extraction is completed, when the product is extruded with the product expulsion rod, air is expelled from the expulsion rod,
The method for producing a powder molded article having an undercut portion according to claim 1, 2, 3, 4, 5 or 6, wherein the powder on the die and the cam die is blown off. 8. The method for producing a powder molded product having an undercut portion according to claim 1, 2, 3, 4, 5, or 6, wherein the powder is sucked by a vacuum from a dispensing rod. 9. An apparatus for producing a powder molded article having an undercut portion, wherein a die having a die hole filled with powder is divided into a plurality of pieces with an undercut portion, and an undercut is provided between divided surfaces. A device for manufacturing a powder molded product, wherein a cam die corresponding to the shape of the portion is provided, and the cam die is configured to be movable back and forth with respect to the die hole.