Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
  • B22F7/06—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools
  • B22F7/08—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools with one or more parts not made from powder
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/12—Both compacting and sintering
  • B22F3/1208—Containers or coating used therefor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
  • F01L1/02—Valve drive
  • F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
  • F01L1/047—Camshafts
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L2301/00—Using particular materials
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L2303/00—Manufacturing of components used in valve arrangements
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49229—Prime mover or fluid pump making
  • Y10T29/49293—Camshaft making
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/4998—Combined manufacture including applying or shaping of fluent material
  • Y10T29/49982—Coating
  • Y10T29/49984—Coating and casting

Definitions

• the invention relates to a method for producing a tubular camshaft, in particular for an internal combustion engine, in which individual cams are subsequently applied to a prefabricated tubular shaft.
• Camshafts are usually cast solidly; the cams themselves are brought to their nominal size by turning and grinding. In recent years, light and hollow camshafts have been required with regard to multi-valve technology. This favors central lubrication in terms of construction and allows material savings. Recently there have been practical approaches for assembling the camshafts from individual segments. Individual tubular shaft segments are assembled with finished cams to form the overall shaft, or individual cams are attached to a one-piece shaft tube and connected to it by gluing, soldering or mechanically. A large number of methods have been described for connecting a hollow shaft and prefabricated cams and possibly bearing elements.
• cams As a specific method for applying the cams on the shaft u. a. soldering in connection with pipe expansion described above (DE-OS 34 31 361). To increase the clamping effect and to achieve a high-strength solder connection, the cams are serrated on their inner circumferential surface.
• a cast camshaft is made of a uniform material.
• the cams which are exposed to particular wear are often additionally surface-treated or are given a particularly wear-resistant and abrasion-resistant surface protective layer.
• different materials can be used for tubular parts with attached cams for both parts (DE-OS 23 36 241).
• sintered, sinter-forged, cast, extruded, stamped or also turned and milled parts for the cams placed on the tubular shaft and to firmly adhere them to the shaft by gluing, welding, brazing, shrinking or stretching connect.
• a disadvantage of all of the methods described above for the subsequent application of cams to a shaft is the difficulty or the great technical outlay for pre-processing the cams and for their precise positioning and fixation on the shaft.
• the process coordination of the expansion or shrinking in terms of the materials advantageously used for the tubular shaft and for the cams is also not yet adequately technically solved.
• the choice of materials requires great compromises.
• widening of the tubular shaft generally means that the material flows and thus the formation of different wall thicknesses in partial areas of the tubular shaft.
• the object of the present invention is then to provide a process which is technically less complex and therefore more economical than the prior art for producing a tubular camshaft using a prefabricated tubular shaft to which cams and possibly other bearing or wearing parts are subsequently applied.
• the inventive method should in particular enable the construction of very light camshafts with shafts that are as thin as possible. Selection criteria for the materials of the shaft and cam should primarily be an optimization of the required mechanical strengths and wear resistance, which differ in individual areas of the camshaft, without compromise with regard to the manufacturability that has only been possible until today.
• cam material is pressed and sintered onto the prefabricated, tubular shaft as a powder, that the shaft and the cam material are introduced into a lost press sleeve and are isostatically pressed in this arrangement by means of a pressure medium, and that the pressure medium continues to be used receives free access to the inside of the pipe during the pressing process.
• the inventive method is primarily used for the production of metallic camshafts, but is not limited to these versions.
• the use of hard metals, of metal-ceramic or even purely non-metallic materials is conceivable.
• a material A in the form of a comparatively thin layer into the press cover in the area of the cams and then to fill the cam area of the press cover with a powdery material B.
• Material A can, for example, be injected into the mold in a mixture with an adhesive which can be evaporated later, or it can also be introduced in the form of metallic cloths, ie in the form of a mixture of wear-resistant material and elastic, evaporable binder material.
• the plastic blow molding process is now a widespread economic process, according to which a large number of plastics, in particular polyethylene, are extruded into a tube-like raw form and then, in the not yet hardened state, are pressed against a mold wall and cured by means of compressed air.
• plastics in particular polyethylene
• the pressure medium is primarily water. This results in an average compression shrinkage of 15-25% of the powder material poured into the casing and slightly pre-compressed by shaking.
• the press cover is still like this to dimension that it bears positively on the tubular shaft outside the cam areas and thus prevents an undesirable eccentricity of the camshaft.
• the pressing sleeve is advantageously mechanically opened by means of a metallic sleeve of the shaft surface in the end area.
• the unimpeded access of the pressure medium to the inside of the tube during the pressing process is desirable, firstly, so as not to deform the comparatively thin-walled shaft tube during the high pressures during the pressing, and secondly to ensure that the pressing of the cam material onto the prefabricated shaft is technically a one-sided pressing and Condense is. This facilitates sufficiently uniform powder compaction and compliance with the desired green compact dimensions.
• the end regions of the prefabricated tubular shaft ie the sections between the shaft end and the first cam, must be long enough to enable a powder-tight seal between the press sleeve and the shaft surface. It may therefore be necessary to cut the initially oversized tubular shaft to length after the pressing process.
• shaft ends of any configuration pressed separately to green compacts can be pushed onto or inserted into the shaft on the camshaft following the inventive pressing process and sintered onto the shaft in a joint sintering process and materially connected to the shaft via diffusion bonding will.
• a prefabricated tubular shaft made of a comparatively ductile and flowable material, e.g. B. copper, and the shape of the lost press cover dimensioned so that powdered cam material is pressed as a layer on the shaft and then sintered in the area between individual cams.
• the flexural strength of the camshaft is generally determined by the outer wall.
• the shaft is advantageously protected against warping during isostatic pressing by inserting perforated steel tube, at least in sections, into the prefabricated tubular shaft during this process step. The perforation allows the press medium to pass through to the inner tube surface of the prefabricated shaft.
• a "near net shape" shaping can be achieved via the inventive method, i. H. After sintering, the camshaft thus prefabricated only has to be brought to the required surface quality and to the final dimensions within the permitted dimensional tolerances in a final grinding process.
• the plastic press cover is detached or burned off by the compact after the pressing process and is not recyclable.
• the subsequent sintering process takes place according to known methods.
• the camshafts are advantageously sintered hanging vertically.
• post-treatment of the material is necessary to restore the mechanical properties of the shaft material that were lost due to the sintering.
• the tubular prefabricated shaft will be primarily cylindrical. However, it can also have the shape of a polygonal polygon in cross section.
• the prefabricated shaft is advantageously pretreated in accordance with the known prior art in order to facilitate the sintering on of the pressed-on cam material with diffusion bonding with the shaft material.
• Such measures are, for example, sandblasting or phosphatising the surface.
• an intermediate layer from a third material. Mechanical tensions can lead to cracks and, at worst, to detach the cams from the shaft. With regard to shrinkage behavior and thermal expansion coefficient, the properties of the intermediate layer material should lie between those of the cam and the shaft material, or should themselves have high ductility and flowability. Intermediate layers of this type can, for example, be sprayed onto parts of the prefabricated shaft before being introduced into the press cover, applied or pushed on as a shaped sheet with a precise fit.
• the main advantage of the present inventive method compared to the known prior art for the production of tubular camshafts using a prefabricated shaft tube lies in the more economical production, in contrast to the prior art, the selection of materials which is practically unrestricted.
• the economic advantage of the inventive method stems from the fact that lost press sleeves can be produced inexpensively using the plastic blow molding process and yet with great dimensional reproducibility and quality consistency.
• "near net shape" cams can be sintered onto the tubular shaft, which are then brought into the ready-to-use state solely by means of a comparatively inexpensive grinding process.
• the production of camshafts according to the invention and further processing until the product is ready for use is more economical than the production by casting and machining and grinding.
• camshafts become more diverse when using the method according to the invention than when manufacturing according to known methods.
• press cover was closed at both ends - clamped onto the ends of the tubular shaft by means of mechanically lockable sleeves, leaving the pipe ends open - and isostatically pressed at 2500 bar in a cold isostatic press using water as the pressure medium.
• the mold After pressing, the mold was burned off in a protective gas stream in the preheating zone of a sintering furnace, the lost polyethylene press casing decomposing and burning almost without residue. Subsequently, the camshaft freed from the press cover was provided at both ends with a pre-pressed blank green body and suspended in the sintering furnace by means of suitable holders. The sintering under protective gas took place at a temperature of 1080 ° C for 60 minutes. The pressed alloy powder entered into a metallic connection with the pipe material. The hardness of the cams in the sintered state was 52-54 HRC.
• the camshaft could be finished economically by grinding alone.
• a prefabricated tubular shaft made of copper or a low-alloy, comparatively ductile and flowable copper alloy is pushed onto a perforated steel tube of high strength to produce the camshaft for the isostatic pressing process.
• Powder of a wear-resistant steel alloy is introduced as cam material into the lost press cover.
• the composite, perforated steel tube and copper shaft is introduced into one of the two openings of the press cover and pushed through it with shaking and powder compaction.
• the inner dimension of the press cover is such that it fits tightly on both ends of the shaft after insertion of the tubular shaft, but in the remaining areas outside the cams a powder-filled space between the tubular shaft and the press cover wall remains.
• the press cover sits on the ends of the non-perforated steel tube which protrude from the copper tube and fits over a sufficient length.
• the ends of the press cover are clamped onto the pipe surface by means of sleeves and introduced into an isostatic press in such a way that the press medium can also penetrate into the pipe end and there act on the tubular shaft made of copper through the perforated steel shaft.
• the powder material is pressed both through the press cover and via a slight expansion of the copper tube.
• the perforated steel tube is pulled out of the copper tube again. This is usually done effortlessly due to the slight expansion of the copper tube during the isostatic pressing process.
• the camshaft freed from the press cover is sintered in accordance with the conditions of Example 1, but at temperatures which are lower by approximately 100 ° C.
• the sintered camshafts are then finished by mechanical grinding.
• This embodiment of the method enables particularly good and elastic connections to be achieved between the prefabricated tubular shaft and the sintered-on material.
• Material tests have shown that flowable copper already penetrates into the pores between the powder grains in a transition zone during the pressing process and this material crosslinking is further reinforced by interdiffusion during the subsequent sintering process. This makes it possible to achieve particularly firm and at the same time elastic connections between the prefabricated tubular shaft and the cam material. Camshafts manufactured in this way showed no tendency to crack.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Materials Engineering (AREA)
• Gears, Cams (AREA)
• Powder Metallurgy (AREA)
• Valve-Gear Or Valve Arrangements (AREA)
• Manufacturing Of Tubular Articles Or Embedded Moulded Articles (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=6364749

Family Applications (1)

Country Status (4)

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Family Cites Families (18)

• 1988
  • 1988-10-10 DE DE3834401A patent/DE3834401A1/de active Granted
• 1989
  • 1989-10-03 JP JP1258651A patent/JPH02141506A/ja active Pending
  • 1989-10-05 EP EP89202500A patent/EP0364028B1/de not_active Expired - Lifetime
  • 1989-10-05 DE DE8989202500T patent/DE58901036D1/de not_active Expired - Lifetime
  • 1989-10-06 US US07/418,123 patent/US5016348A/en not_active Expired - Fee Related

Non-Patent Citations (1)

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