EP0682999B1 - Article molded from metal powder and process and apparatus for preparing the same - Google Patents

Description

The invention relates to a metallic sintered part, with at least one across to the undercut lying in the pressing direction, together with the method and device for its production with the Features of the preambles of the independent claims 14, 1 and 8, which are based on US-A-4 164 063.

A sintered metal body is known from DE-OS 37 34 002, the undercuts lying transverse to the pressing direction having. To form the undercuts is the sintered metal body is made up of several parts. The single ones molded parts are put together to form a component and then by applying a layer of magnetite bonded together on their surfaces. This procedure requires due to the multiple parts of the sintered metal body a certain and procedural effort. The undercuts can also through machining into the sintered metal body be introduced. Furthermore, the possibility addressed, the individual parts of a multi-part Unite sintered metal body by welding or soldering. These techniques also mean one increased construction and process costs, which is in the Costs and in the economics of manufacturing Pressed part disadvantageously precipitates.

It is an object of the present invention to provide a pressed part, in particular a powder metallurgy Sintered part to show the disadvantages described above does not have as well as a manufacturing process and a Specify the device with the help of the undercuts having pressed and sintered parts made of metal powder easier and be produced more economically than before can.

The invention solves this problem with the features in the Material, procedural and device claims hereby be inserted into the description.

The powder-metallurgical method according to the invention Pressed or sintered part is characterized by integrally formed undercuts, i.e., the Undercuts are preferred in a pressing process when calibrating, to a pre-pressed one-piece Blank molded. The blank lies in the case of a sintered part already in the sintered state. The above procedure leaves a combination of previously separate pressed individual parts and / or elaborate post-processing omitted. Due to the one-piece of the blank tolerance problems that e.g. by adding an existing oversize or undersize parts to be joined, avoided. In addition, the invention Process faster, easier and cheaper carry out.

For the shaping of the undercuts the last one There are various pressing or calibration processes Possibilities. In the preferred embodiment the undercuts on the blank when calibrating molded by material shift. At the same time the blank is compacted. For example, also a stamp or slide across the blank press and press in the undercut.

In the preferred embodiment, the bottom of the However, undercuts due to the basic shape of the existing one Blanks formed and calibrated for everyone Undercut just a protruding shoulder molded. This is preferably done by an im Blank material stock is moved, creating a protruding shoulder for the undercut is molded.

The material is preferably moved by a movable stamp, which in the appropriate place existing material in the blank transverse to the pressing direction in a lateral recess on a die displaced, thereby forming the aforementioned shoulder. The material stock is at least equal in volume large as the recess and both, the material supply and the recess are arranged adjacent. Preferably the material stock is somewhat larger in volume than the recess.

According to a preferred variant, the Material supply in the form of an elevation on the surface the blank in the neighborhood of the shoulder later forming recess in the die. To Another preferred variant is the Material stock in the blank and is used for pressing or Calibrate by penetrating one located on the press ram Intent shifted into the blank. The volume the resolution is at least as big as that later the shoulder-forming recess.

The process according to the invention can be carried out in a conventional manner Carry out pressing device. However, there must be one the die adapted to the molding task can be used. This has two or more movable jaws or segments, at least one / one on the pressing surface Recess has the shape and volume of the later the undercut projecting shoulder corresponds. For demolding the finished and calibrated pressed part the die can be opened, which also enables the die Undercut is released.

The method according to the invention is described in the following its entire process based on the variant in which the material reservoir in the form of a survey the surface of the blank is described. First, a pre-product body is made by powder metallurgy manufactured in which there is an area which is adjacent to the later undercut and which is transverse to the pressing direction during calibration Material reservoir is located, the volume of which is at least corresponds to the volume in the finished sintered body the undercut protruding and limiting shoulder occupies. After that, the pre-product body is turned into an matrix consisting of at least two movable segments, which are caused by moving the segments apart in the open Condition, inserted. This matrix has on its inner wall at least one recess that the intended form of at least one, in the finished Sintered metal part protruding and undercut limiting shoulder is equivalent. The intermediate product body is inserted into the die in such a way that the material reservoir area at the point is located on the corresponding one in the inner wall of the die Recess for the formation of the undercut towering shoulder. Then the Matrix with the pre-product body in at least one a die press having a punch in the pressing position brought, the matrix by means of e.g. hydraulic or mechanically acting locking device Press the segments together to the calibration dimension and the pre-product body with a ram under Application of such a pressure calibrated that on him or material reservoir located in it through flow processes into the recess in the die wall is rearranged and thus the undercut outstanding and limiting bulge arises. To this pressing process is the ram from the die removed that spanning the die segments Closing device relieved or removed, it will Die segments moved outwards in the open position and the finished pressed part is removed.

In the subclaims, which are also part of the description are considered, are advantageous embodiments the pressing device described. On the one hand, this affects a die that is two or more transverse to the pressing direction has movable jaws or segments and the other a conical clamping ring, which is used for an automatic and tight locking of the movable jaws of the die when calibrating. Furthermore, are different designed press ram provided for targeted shaping variants make on the finished pressed part can.

The pressed part or the blank can be made of any suitable metal powder exist. It has proven to be beneficial proven if the blank material has an elongation at break of more than 2%, preferably more than 10%. Suitable materials are e.g. SINT D35 (containing phosphorus Steels), SINT D40 (stainless steel) etc.

Figur 1 und 2 :

das fertige Preß- oder Sinterteil mit Hinterschneidungen in Draufsicht und im Längsschnitt,

Figur 3 und 4 :

den Verformungsgang eines Rohlings beim Ankalibrieren der Hinterschneidung im Halbschnitt längs,

Figur 5 und 6 :

eine Variante zu Figur 3 und 4 und

Figur 7 bis 11:

die Preßvorrichtung in verschiedenen Arbeitsstellungen und Ansichten.

The invention is illustrated by way of example and schematically in the drawings. In detail show:

Figure 1 and 2:

the finished pressed or sintered part with undercuts in top view and in longitudinal section,

Figures 3 and 4:

the deformation path of a blank when calibrating the undercut in half-cut lengthways,

Figure 5 and 6:

a variant of Figure 3 and 4 and

Figure 7 to 11:

the pressing device in different working positions and views.

1 and 2 show a finished pressed part 7 made of metal powder, preferably in the form of a sintered part. It is preferably made of an alloy steel, but can any other suitable metallic Have composition.

The finished pressed or sintered part consists of one Metal that has an elongation at break of more than 2%, preferably has more than 10%. Suitable materials are e.g. SINT D35 (phosphorus-containing steels) or SINT D40 (stainless steels).

The finished press part 7 has at least one transverse to Pressing direction undercut 3. In the shown Embodiment is two 180 ° opposite undercuts 3 in shape of transverse grooves or troughs. Figure 2 illustrates the training in longitudinal section. The Undercut 3 has a bottom 4 and a projecting one Shoulder 5. The counter shoulder is through here a widened head plate 6 is formed.

The pressing part 7 can be designed in any other way his. It can also be an undercut 3 or only three or more undercuts 3 or an annular groove have, which also distributed arbitrarily on the pressing part 7 can be / can be.

The finished part 7 receives the undercuts 3 at Calibration of a pre-pressed, in the case of a sintered part one pre-pressed and sintered, from only one Part of existing blank 2 by molding. As the Figures 3 to 6 illustrate the shoulders 5 formed by material shift. The calibration process takes place in a press device 1, the below with reference to Figures 7 to 11 in more detail is described and shown.

The blank 2 has a simple, by pressing optionally powders provided with a binder and preferably subsequent sintering easy to manufacture Shape. In the exemplary embodiment shown, it already has the Head plate 6 and a smooth shaft or pin 22, the the approximately barrel-shaped cross section shown in Figure 1 having. The blank 2 has no finished Undercut 3 transverse to its pressing direction. The However, side walls of the shaft or pin 22 form already the later floors 4 of those shown in Fig. 4 Undercuts 3.

As shown in FIGS. 3 to 6, the blank 2 Material stocks 8, which are shifted during calibration and thereby form the new shoulders 5.

In Figure 3, the material stocks 8 consist of in the pressing direction 19 protruding protrusions 9. The protrusions 9 are in the pressing device 1 by a stamp 12th flattened, the material stock transverse to the pressing direction 19 deflected and in lateral recesses 16 a die 14 are displaced. The shape of the recesses 16 correspond to the shoulders to be formed 5. The Stamp 12 forms the surfaces of the shoulders 5. Figure 4 shows the shape of the finished pressed part with the undercuts 3 and the molded shoulders 5.

In the exemplary embodiment in FIG. 5, the blank 2 no head start 9. The material stocks are here in the Basic shape of the blank integrated and therefore not separate shown. The stamp 12 has on the top two bump-like profiles 13, which during calibration leave a depression 20 in the finished pressed part 7. Due to the oblique flanks of the profiles 13 the material of the blank is calibrated in the relevant edge areas of the pin to the side in the Recesses 16 displaced. This results in the Figure 6 shown final form enclosed by the pressing tool of the press part 7.

There are mixed forms between the exemplary embodiments shown and modifications possible. The lower stamp 12 can also in the embodiment of Figure 3 in Press direction 19 have the above profile. Otherwise, the stamp 12 can have any surface design own other shaping options to take into account when calibrating.

The volumes of the recesses 16 essentially correspond the volumes of the material stocks 8 or the projections 9. The volumes of material stocks are preferred 8 a little larger than the volume of them respectively assigned recesses 16, around which, 16, to ensure safe filling.

Figures 7 to 11 show the pressing device 1 in individual. It consists of the aforementioned lower stamp 12, a die 14 with a lateral receptacle or Guide 21, an upper punch 10 and a clamping ring 11.

Demould the finished press part 7 after calibration To be able (Fig. 11), the die 14 is in two or more Jaws 15 divided, which are essentially transverse to the pressing direction 19 are movable (Fig. 8, 8a). Like the figures 8 and 8a illustrate is between adjacent jaws 15 each clamped a spring 18, which the jaws 15 pushed apart. The die 14 can thereby open automatically. The invention also extends to other opening mechanisms.

To close the die 14 and to press it on Jaws 15 is a clamping ring 11 is provided on the Holding plate 23 of the upper punch 10 elastic, e.g. about Springs, is attached and encloses this, 10, on all sides. The jaws 15 are in turn in a side Recording 21 kept movable. The clamping ring 11 has an internal conical clamping surface 17, which extended to the die 14. The die 14 or its Jaws 15 in turn have a counter cone Coat 24. When the upper stamp 10 with the Clamping ring 11 is lowered according to FIGS. 7 to 10, the clamping ring 11 engages over the jaws 15 and presses them radially together.

The lower stamp 12 protrudes through the lower one, in the lateral one Recording 21 guided and movable in this Recording 26 and is guided centrally in the die 14. As shown in Figures 3 to 6, the Recess 16 continues downward and serves with their lateral Limits as a guide surface for the lower stamp 12. Depending on the desired shoulder shape, the Recess 16 the shape of a straight or curved groove or another suitable form such as a Have ring groove. Several recesses 16 can also be made the press axis 19 can be arranged distributed around. The Recesses 16 are located on the inside of the Die jaws 15.

During calibration, the blank 2 is placed on the desired one Gauge blocks of the pressed part 7 brought and also in compressed substantially uniformly.

Figure 7 shows the starting position of the open Pressing device 1. The blank 2 is opened Die 14 inserted. The embodiment shown corresponds Figure 3.

Then (Fig. 9) the upper stamp 10 with the Collet 11 lowered so far that the die 14 in the is closed as described above. Then the Upper stamp 10 by means of its holding plate 23 under partial Compression of the between the holding plate 23rd and the clamping ring 11 located springs 25 on the Head plate 6 of the blank 2 driven, the on the Segments 15 of the die 14 further acting closing pressure is increased. In the following calibration process (Fig. 10) will further increase the calibration force the whole of the holding plate 23 for the upper stamp, Upper punch 10, clamping ring 11, die 14 and lower Recording 26 existing arrangement against the standing Lower stamp 12 lowered. The side shot or Guide 21 for the die 14 and the clamping ring 11 remains thereby stationary. In this process, the material stocks 8 displaced into the recesses 16 (Fig. 9), the Shoulders 5 of the undercuts 3 and the Blank calibrated to the final dimensions of the finished part 7.

In the last step according to FIG. 11, the Stamp 10 with the clamping ring 11 raised again. Hereby open by the pressure of the springs 18 (Fig. 8, 8a) automatically give the jaws 15 of the die 14 and the compact 7 free. By lifting the lower punch 12 the compact can be ejected. He can also on otherwise removed from the die 14.

Modifications of the described embodiments are possible in different ways. For example, a transverse slide should be installed, which on the Blank presses and presses the undercut. Further can the punches 10, 12 and the die 14 opposite the embodiment shown a different shape to have. For example, when calibrating both the shoulder as well as the back shoulder of an undercut be molded on. For this purpose the Upper stamp 10 in a similar manner to the lower stamp 12 be formed, the die 14 also in the upper Area has lateral recesses 16.

Furthermore, the locking mechanisms for the die segments 15 be different. For example eccentric or toggle lever systems can be used or hydraulic cylinders perform the locking function.

Reference list

1

Pressing device

2nd

blank

3rd

Undercut

4th

ground

5

shoulder

6

Counter shoulder, headstock

7

Pressed part, sintered part, finished part

8th

Material stock

9

head Start

10th

Stamp, upper stamp

11

Tension ring

12th

Stamp, lower stamp

13

Profiling

14

die

15

Cheek, segment

16

Recess

17th

Clamping surface

18th

feather

19th

Pressing direction

20th

trough

21

side mount, guide for 11

22

Shaft or tenon

23

Holding plate for upper stamp

24th

Outer jacket of the die (counter cone)

25th

Feathers between 23 and 11

26

lower receptacle in the pressing device 1

Claims (16)

1. A method of producing a sintered product, for which a one-piece blank is shaped from metal powder in a pressing process and is then sintered, the finished sintered product comprising at least one undercut (3) disposed perpendicularly to the pressing direction, characterised in that the undercut is formed by a projecting shoulder (5) and the shoulder (5) is formed on the sintered blank by reshaping by means of material displacement by sizing during an additional pressing process to yield the finished sintered product.
2. A method according to claim 1, characterised in that the projecting shoulder (5) is formed by sizing, the bottom (4) of the undercut (3) being formed by the basic shape of the sintered blank (2).
3. A method according to one of claims 1 to 2, characterised in that, in sizing, a punch (12) pushes the material of the sintered blank (2) intended for the purpose perpendicularly in relation to the pressing direction (19) into a recess (16) located in an internal wall of a mould (14), to form the projecting shoulder (5).
4. A method according to one of claims 1 to 3, characterised in that a blank (2) is produced with reserve material (8), the volume of the reserve material (8) corresponding substantially to the recess (16), and in that the sizing process is performed using the reserve material (8).
5. A method according to one of claims 1 to 4, characterised in that the reserve material (8) takes the form of a projection (9) protruding in the pressing direction (19) on the blank (2), and this projection is pressed, during sizing of the sintered blank (2), into the latter and, as a consequence of displacement processes, laterally into the recess (16).
6. A method according to one of claims 1 to 5, characterised in that the reserve material (8) is present in the basic shape of the blank (2) and is pushed during sizing laterally into the recess (16) by projecting profiling (13) on the punch (12), forming a trough (20) on the side of the blank (2) facing the punch (12).
7. A method according to one of claims 1 to 6, characterised in that at least one undercut (3) is pressed in by a slide acting perpendicularly to the pressing direction (19).
8. A device for producing sintered products having at least one projecting shoulder (5), which forms an undercut (3) located perpendicularly to the pressing direction, using the method according to claims 1 to 7, characterised by a pressing device (1), with at least one movable punch and one mould, the mould (14) comprising at least two jaws (15) movable substantially perpendicularly to the pressing direction (19), of which jaws (15) at least one comprises at least one recess (16) on a pressing surface.
9. A device according to one of claims 1 to 8, characterised in that the punch (12) forming the undercut (3) comprises profiling (13) projecting in the pressing direction (19).
10. A device according to one of claims 1 to 9, characterised in that the profiling (13) comprises at least the same volume as the associated recess (16).
11. A device according to one of claims 1 to 10, characterised in that the pressing device (1) comprises a clamping ring (11), which engages over the mould (14) during sizing, surrounds it firmly and presses the jaws (15) of the mould (14) together against the internal pressure prevailing in the mould (14).
12. A device according to one of claims 1 to 11, characterised in that the clamping ring (11) comprises a conical clamping surface (17) and the mould (14) comprises a mating cone (24) at the outer surface.
13. A device according to one of claims 1 to 12, characterised in that the clamping ring (11) is arranged on a movable upper punch (10).
14. A metallic sintered product having at least one undercut (3) located perpendicularly to the pressing direction, produced by the process according to method claims 1 to 7, characterised in that the undercut (3) is formed by reshaping of a one-piece pressed blank by an additional sizing pressing process to yield the finished product.
15. A metallic sintered product according to claim 14, characterised in that the undercut (3) comprises a bottom (4) and a projecting shoulder (5), a counter-shoulder being formed by a top plate (6).
16. A metallic sintered product according to claim 14 or 15, characterised in that the material of which the sintered product consists exhibits elongation at break of greater than 2 %, preferably greater than 10 %.

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