Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Patent
1996-07-12
1998-12-22
Luong, Vinh T.
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
74567, 29525, C21C 704
Patent
active
058506950
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/DE 94/01213, filed Oct. 14, 1994.
BACKGROUND OF THE INVENTION
The invention relates to a hollow camshaft as well as a process for producing hollow camshafts by employing internal high pressure shaping of hollow pipes.
The invention in particular relates to processes employing pre-shaping in the course of internal high pressure shaping for designing complete hollow shafts from pipe sections, wherein pipe sections are here understood to be arbitrary long hollow bodies, i.e. also square pipes, hexagonal pipes or other hollow profiles.
In comparison with solid hollow shafts, hollow camshafts, such as schematically represented in FIG. 1, offer a weight advantage of up to 75% over shafts of solid material. In comparison to this, constructed camshafts such as known from DE-37 04 092, EP 278292, DE-3428372 or EP 290758 or EP 303845, only offer a weight advantage of 40% in comparison with solid shafts. In addition, constructed camshafts are comparatively expensive to produce, because separate cams and hollow pipes must be stocked and then placed together in a die in a suitable manner. Thus, expensive individual components must be kept in stock and combined.
For this reason hollow camshafts, although their constructed shape has been described theoretically and also in patent applications, have not yet been used in motor vehicles up to now.
The reason for this lies in a suitable process technique for producing these shafts.
Suggestions for producing constructed hollow camshafts are recited, for example, in DE-19 10 517. These process techniques are, however, completely unusable for producing hollow camshafts from pipe sections. The required degrees of shaping can not be achieved by electromagnetic or by electro-hydraulic shaping. Swaging or round kneading as described in DE-37 36 453 also has not met the goal. This method of producing hollow camshafts fails particularly because of the one-sided mass distribution in the cams. The one-step internal high pressure shaping by means of a tool in accordance with U.S. Pat. NO. 2,892,254 also does not meet the goal. Although axial feeding of material is provided with this mode of operation, filling the die at the cam tips is not achieved and a considerable stretching of the walls of the cams results. FIG. 2 shows the undesired stretching of the walls on a cam which was produced by means of the known one-step internal high pressure shaping method.
The internal high pressure method or IHV method is here understood to mean the method which was described for example in the Industrieanzeiger seq.: A. Ebbinghaus "Prazisionswerkstucke in Leichtbauweise, hergestellit Construction, Produced by Internal High Pressure Shaping!, or in 243: A. Ebbinghaus "Wirtschaftliches Konstruieren mit Means of Precision Workpieces Produced by Internal High Pressure Shaping!, or "Werkstoff und Betrieb"122, 11, (1989), pp. 933 to 938: A. Ebbinghaus To avoid repetition, reference is made in full to their disclosure in what follows.
These processes have been used up to now for example for producing flanges, as described in EP-2395052, or for producing constructed hollow camshafts for fastening cams on a pipe for producing hollow camshafts.
SUMMARY OF THE INVENTION
In contrast to this it is the object of the invention to provide a hollow camshaft which can be economically produced, and a process for manufacturing it.
This object is attained by means of a one-piece camshaft consisting of metal or plastic which can be cold-shaped and heat-treated and has a flow of fibers which is parallel to the outer contours of the camshaft.
Carbon-containing steel, which can be sufficiently stretched, but can also be heat-treated for hardening, can preferably be used as the material for this.
Suitable materials can be: 19MnB4, 16MnCr5, CK45, 19CrKo44, 15Cr3, C25-steel, X3NiCoMoTilB 9 5, .beta.-C-titanium alloys and those showing similar properties.
The invention furthermore relates to a method for producing hollow shafts, employing the internal high pr
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Saving Manner!. et seq.: A. Ebbinghaus Prazisionswerkestucke in Leichtbauweise, Lightweight Construction, Produced by Internal High Pressure Shaping!. A. Ebbinghaus, Wirtschaftliches Konstruieren mit innenhochdruckgeformten Workpieces Produced by Internal High Pressure Shaping!. Technology!.
Bogel Helmut
Klaas Friedrich
Cosma International Inc.
Luong Vinh T.
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