Oil pump

Abstract

Certain preferred embodiments of the present invention provide an oil pump which is both light as well as compact. Accordingly, certain presently preferred embodiments disclose an oil pump having a housing comprising aluminum, and at least one mobile molded part therein. The mobile molded part being at least partially made from a sinterable composition comprising at least one austenitic iron-based alloy powder. The mobile molded part also has a heat expansion coefficient, which amounts to at least 60% of the heat expansion coefficient for the oil pump housing.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of PCT / EP2004 / 004702 filed May 4, 2004, which claims priority to German Application Number 103 21 521.2 filed May 14, 2003, each of which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION [0002] The present invention relates to molded parts, methods for producing such molded parts, and oil pumps having a housing and at least one such molded part, movably arranged in said housing. BACKGROUND OF THE INVENTION [0003] Oil pumps of the type mentioned at the outset are particularly used in internal combustion engines, in which higher temperatures are dominant. Conventional oil pumps according to prior art are provided with a housing made from cast iron and mobile molded parts arranged therein, for example a toothed set of rotors in the case of an internal gear pump. [0004] Conventional mobile molded parts are usually made from a ferriferous alloy via a sintered metallurgical producti...

AI Technical Summary

Benefits of technology

[0009] The oil pump, according to the certain preferred aspects of the present invention, provides minimal gap leakage during operation in an internal combustion engine. Therefore, larger dimensions are not necessary and, by the use of aluminum, the oil pump housing weight is considerably reduced. The housing of the oil pump can either be made in a casting process or via sinter-metallurgical production methods. The housing is preferably cast from an aluminum alloy.

[0012] The oil pump mobile molded parts of the present invention exhibit a Brinell-hardenss, according to DIN EN 24498-1, of at least 100 HB, preferably 120 HB, more preferred at least 130 HB, still more preferred at least 140 HB. Here, the Brinell-hardness is determined via a hardened steel ball used as an inserted body having a diameter of 2.5 cm and a weight of 62.5 kg. Using such hard mobile molded parts can achieve a long life for the oil pumps according to the present invention. It must be considered that the heat expansion coefficient of conventional aluminum cast alloys range from approximately 20 to 24 ppm, while the heat expansion coefficient of preferred sinterable austenitic iron-based alloys used can be below that of conventional aluminum cast alloys.

[0013] Preferably, the heat expansion coefficient of the mobile molded parts, produced from the material that can be sintered ranges from approximately 12 to approximately 21 ppm, preferably from 16-19 ppm. Using such mobile molded parts it is ensured that the oil pump according to the invention fulfills the mechanical tribological requirements, in particular for use in an internal combustion engine. Preferably, the mobile molded parts of the oil pump comprise a set of rotors, with the axial play (i.e., distance) between at least one rotor of the set of rotors arranged on a shaft and the wall of the oil pump housing, against which the rotors operates, preferably amounting to less than 50 μm, preferably less than 40 μm. Therefore, the oil pump, as a presently preferred embodiment of the invention, can advantageously be constructed in a very compact manner. Furthermore, the axial play defined in the above-described manner achieves high performance of the oil pump in accordance with certain preferred aspects of the present invention.

Problems solved by technology

The use of cast iron and iron-copper alloys results in such pumps having a relatively high weight.

However gap leakage is problematic in such oil pumps, particularly during operation in an internal combustion engine because of environmental temperature variations and generally high temperatures.

However, increasing the pump dimension is counterproductive since the desired weight savings are offset by the increased size of the oil pump.

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