Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1998-09-28
2000-09-05
Batten, Jr., J. Reed
Metal founding
Process
Shaping liquid metal against a forming surface
164105, 164108, B22D 1904
Patent
active
061128031
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for producing cylinder heads for internal combustion engines.
In the manufacture of cylinder heads it is currently known to draw valve seat rings and valve guides with a defined operational density into corresponding bores of the cylinder head after casting of the latter from aluminum or grey cast iron has been completed. In addition, efforts are being made to treat the cylinder head material of the surface of the valve seat in order to meet the high engine stresses.
The known method of drawing in valve seat rings or hollow cylindrical valve guides requires considerable expenditure in terms of production engineering, for example machining of the valve seat ring, valve guide and cylinder head in order to maintain the required installation tolerances, and, furthermore, correct positioning before the rings or valve guides are installed in the cylinder head. In a surface treatment, for example by laser remelting or alloying, substantial amounts of energy are required which, with an efficiency of the laser of 3%, make this method appear very uneconomical.
Furthermore, efforts have been made to cast valve seat rings with high density into cylinder heads. However, no intimate bond is produced in this process between the cylinder head material and the valve seat ring (DE 39 37 402 A1). The ring is substantially retained in the cylinder head only by mechanical clamping, which produces no intimate contact with the cylinder head and thus poses the risk that the rings drop out. This solution, moreover, has the drawback of an oxidized transition from the valve seat ring to the cylinder head; the layer formed in this connection has an insulating effect and prevents high conducting heat transfer.
The objective of the invention is to eliminate said drawbacks. Accordingly, the present invention produces cylinder heads where the expenditure in terms of production engineering is reduced by directly pouring in valve seat rings and valve guides while it is nonetheless possible to obtain intimate bonding of the valve seat rings and valve guides to the cylinder head material and to thus achieve an increase in the thermal conductivity.
According to the invention the solution to said problem consists in a process for producing cylinder heads for internal combustion engines.
Valve seat rings and valve guides with an open pore volume of 5% to 15% are employed in the process as defined by the invention. In the course of the casting process for producing the cylinder head, for example by low-pressure casting, liquid aluminum penetrates the pores of the tempered valve seat rings and valve guides and fills said pores. An intimate bond between the two materials is produced in this process. If aluminum is used as cylinder head material, the thermal conductivity of the materials rises by the proportion of the infiltrated aluminum. In addition, an insulating layer is avoided within the region of the cylinder head and valve seat ring or valve guide, which increases the conduction of heat from the afore-mentioned component to the cooling circulation in the cylinder head. Cutting production steps can be dispensed with both in the working of the cylinder head and in the production of the valve seat rings and valve guides.
The invention also offers the possibility for using ceramic materials instead of the conventional seat ring and guide materials based on iron or copper, such ceramic materials being specially conceived for infiltration by liquid light metals.
Liquid aluminum can be poured into the mold either under force of gravity or under pressure, if need be with variable pressure conditions.
It is useful to heat valve seat rings and valve guide prior to pouring. This can be carried out either together with the mold after placing said components in the latter, or before placing said components in the mold.
According to an advantageous further development it is possible to adjust the pore volume of valve seat rings and valve guides in a graduated manner, i.e., in a manner such that the area with high therma
REFERENCES:
patent: 3167854 (1965-02-01), Schafer, Jr.
patent: 3939897 (1976-02-01), Kaneko et al.
patent: 4688527 (1987-08-01), Mott et al.
Abstract of Japanese Patent Publication 60-203353 Published Oct. 14, 1985.
Abstract of Japanese Patent Publication 61-115657 Published Jun. 3, 1986.
Batten, Jr. J. Reed
Bleistahl Produktions-GmbH & Co. KG
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