RELIEF VALVE FOR A TURBOCHARGER AND PROCESS FOR MANUFACTURING A RELIEF VALVE

Abstract

The present invention relates to a relief valve (1) for a turbocharger, in which the crank arm (3) is made of a first material and the shaft (4) is made of a second material different from the first material used for manufacturing the crank arm (3), each of the materials containing a composition that provides the necessary properties according to the application of each component of the relief valve (1). The present invention also relates to a process for manufacturing the relief valve (1), which allows the crank arm (3) and the shaft (4) to be manufactured separately, using different materials for the manufacture of each component.

Claims

1-15. (canceled)

16. A relief valve (1) for a turbocharger, the relief valve (1) comprising: a valve flap (2); and a support element, the support element being formed by a crank arm (3) and a shaft (4), wherein: the crank arm (3) is made of a first material; and the shaft (4) is made of a second material different to the first material used for manufacturing the crank arm (3).

17. The relief valve (1) according to claim 16, wherein the first material used for manufacturing the crank arm (3) is composed of a nickel-based material with at least 30% nickel by weight.

18. The relief valve (1) according to claim 17, wherein the first material used for manufacturing the crank arm (3) contains up to 0.08% carbon by weight, 0.5% silicon by weight, up to 0.5% manganese by weight, up to 0.015% phosphorus by weight, up to 0.01% sulphur by weight, between 13.5% and 15.5% chrome by weight, between 30% and 33.5% nickel by weight, between 0.4% and 1% molybdenum by weight, between 1.6% and 2.2% aluminum by weight, and iron as residue.

19. The relief valve (1) according to claim 16, wherein the first material used for manufacturing the crank arm (3) is composed of an austenitic stainless steel with at least 10% chrome by weight and 15% nickel by weight.

20. The relief valve (1) according to claim 16, wherein the first material used for manufacturing the crank arm (3) contains up to 0.15% carbon by weight, up to 0.75% silicon by weight, up to 2% manganese by weight, up to 0.045% phosphorus by weight, up to 0.03% sulphur by weight, between 24% and 26% chrome by weight, between 19% and 22% nickel by weight, and iron as residue.

21. The relief valve (1) according to claim 16, wherein the second material used for manufacturing the shaft (4) is composed of a nickel-based material with at least 60% nickel by weight.

22. The relief valve (1) according to claim 16, wherein the second material used for manufacturing the shaft (4) contains between 0.04% 0.10% carbon by weight, up to 1% silicon by weight, up to 1% manganese by weight, up to 0.02% phosphorus by weight, up to 0.015% sulphur by weight, between 18% and 21% chrome by weight, at least 65% nickel by weight, between 1% and 1.8% aluminum by weight, and up to 3% iron by weight.

23. The relief valve (1) according to claim 16, wherein the valve flap (2) is made of the first material used in the manufacture of the crank arm (3).

24. The relief valve (1) according to claim 16, wherein the valve flap (2) is made of the second material used in the manufacture of the shaft (4).

25. The relief valve (1) according to claim 16, wherein the valve flap (2), the crank arm (3) and the shaft (4) receive a ceramic coating, PVD or CVD, or a nitriding treatment or a hardening treatment.

26. A process for manufacturing the relief valve (1) as defined in claim 16, the process comprising the steps of: forging the valve flap (2); forging the crank arm (3) and the shaft (4) in separate parts; and carrying out an attrition welding connecting process for the association between the crank arm (3) and the shaft (4).

27. The process according to claim 26, wherein the valve flap (2), the crank arm (3) and the shaft (4) receive a ceramic coating, PVD or CVD, or a nitriding treatment or a hardening treatment.

28. A process for manufacturing the relief valve (1) as defined in claim 16, the process comprising the steps of: forging the valve flap (2); machining of crank arm (3) and the shaft (4) in separate parts; and carrying out an attrition welding connecting process for the association between the crank arm (3) and the shaft (4).

29. The process according to claim 28, wherein the valve flap (2), the crank arm (3) and the shaft (4) receive a ceramic coating PVD or CVD, or a nitriding treatment or a hardening treatment.

30. A relief valve (1) for a turbocharger formed by a valve flap (2) and a support element, the support element being formed by a crank arm (3) and a shaft (4), wherein the relief valve is obtained by a process comprising the steps of: forging the valve flap (2); forging or machining the crank arm (3) and the shaft (4) in separate parts; and carrying out an attrition welding connecting process for the association between the crank arm (3) and the shaft (4).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0022] The relief valve for a turbocharger of the present invention can be better understood by way of the following detailed description which is based on the drawings listed below:

[0023] FIG. 1—schematic representation of a turbocharger with indication of the installation position of the relief valve;

[0024] FIG. 2—representation of a relief valve with all the constituent parts;

[0025] FIG. 3—representation of the microstructure obtained in the connecting portion between the crank arm and the shaft of the relief valve of the present invention;

[0026] FIG. 4—representation of the valve flap of the relief valve of the present invention;

[0027] FIG. 5—representation of the valve flap of the relief valve of the present invention, illustrating the pin associated to the fastening component;

[0028] FIG. 6—representation of the microstructure obtained in the connecting portion between the crank arm and the shaft of the relief valve of the present invention; and

[0029] FIG. 7—graphic representation of the fatigue resistance achieved by a relief valve of the state of the art, represented by the letter A, and the relief valve of the present invention, represented by the letter B.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

[0030] The present invention presents a relief valve 1 for a turbocharger in which the components that form the relief valve 1 are made in separate parts, using different materials for the manufacture of each component. FIG. 1 is a schematic representation of a turbocharger, indicating the position of the relief valve 1.

[0031] Usually, a relief valve is formed by basically two parts, namely a valve flap 2 and a support element, as illustrated in FIG. 2. This support element consists of a shaft 4 and a crank arm 3.

[0032] The relief valve 1 of the present invention presents the crank arm 3 being made of a first material and the shaft 4 being made of a second material different to the first material used for manufacturing the crank arm 3.

[0033] In a first preferred constructive configuration, the first material used for manufacturing the crank arm 3 is composed of a nickel-based material with at least 30% nickel by weight. Particularly, the crank arm 3 is made of a first material which contains up to 0.15% carbon by weight, up to 0.75% silicon by weight, up to 2% manganese by weight, up to 0.045% phosphorus by weight, up to 0.03% sulphur by weight, between 24% and 26% chrome by weight, between 19% and 22% nickel by weight and iron as residue.

[0034] In a second preferred constructive configuration, the first material used for manufacturing the crank arm 3 is composed of an austenitic stainless steel with at least 10% chrome by weight and 15% nickel by weight. Particularly, the crank arm 3 is made of a first material which contains up to 0.08% carbon by weight, 0.5% silicon by weight, up to 0.5% manganese by weight, up to 0.015% phosphorus by weight, up to 0.01% sulphur by weight, between 13.5% and 15.5% chrome by weight, between 30% and 33.5% nickel by weight, between 0.4% and 1% molybdenum by weight, between 1.6% and 2.2% aluminum by weight and iron as residue.

[0035] Regardless of the composition of the first material used for manufacturing the crank arm 3, the shaft 4 should necessarily be made of a second material different to the first material. Preferably, the second material used for manufacturing the shaft 4 is composed of a nickel-based material with at least 60% nickel by weight. Particularly, the shaft 4 is made of a second material containing between 0.04% 0.10% carbon by weight, up to 1% silicon by weight, up to 1% manganese by weight, up to 0.02% phosphorus by weight, up to 0.015% sulphur by weight, between 18% and 21% chrome by weight, at least 65% nickel by weight, between 1% and 1.8% aluminum by weight and up to 3% iron by weight.

[0036] The valve flap 2 is made of a first material, identical to the one used in the manufacture of the crank arm 3, or of a second material, identical to the one used in the manufacture of the shaft 4. The selection between the first or the second material for manufacturing the valve flap 2 varies according to each project and application.

[0037] Among the processes used for manufacturing the relief valve 1 of the present invention, forging and machining are prominent, followed by a connecting process carried out by attrition welding.

[0038] In a first preferred constructive configuration, the valve flap 2, the crank arm 3 and the shaft 4 are made separately by means of a forging process. The valve flap 2 and the crank arm 3 are associated by means of a pin, whereas the crank arm 3 and the shaft 4 are connected by a process of attrition welding.

[0039] The process of forging per se achieves superior mechanical properties compared to the process of investment casting, used in the state of the art, since it provides greater dislocation density and prevents the formation of microporosities, increasing the robustness of the components.

[0040] In turn, the process of attrition welding is capable of refining the microstructure of the connecting portion 5 between the crank arm 3 and the shaft 4, enhancing the mechanical properties in this connecting portion 5 and, chiefly, increasing the robustness against breakages. FIG. 3 illustrates the refined microstructure obtained in the connecting portion 5 subjected to the process of attrition welding.

[0041] Additionally, the fact that each one of the components of the valve is made separately enables the use of different materials in manufacturing the components, enabling the selection of optimized materials specifically for obtaining different properties.

[0042] For example, the first material selected for manufacturing the crank arm 3 achieves specific properties for providing an increase in resistance to high temperatures and resistance to corrosion. In contrast, the second material selected for manufacturing the shaft 4 provides specific tribological properties.

[0043] Alternatively, in a second preferred constructive configuration, the valve flap 2, the crank arm 3 and the shaft 4 are made separately by means of a process of machining, with the valve flap 2 and the crank arm 3 being associated by means of a pin, whereas the crank arm 3 and the shaft 4 are connected by a process of attrition welding.

[0044] The high resistance to breakage, obtained in the connecting portion 5 between the crank arm 3 and the shaft 4, is proven by carrying out a fatigue resistance test by using a vertical pulsating machine on a test bench.

[0045] For the test, a comparison was made of two relief valves having identical designs. However, for the relief valve 1 from the state of the art, indicated by letter A, a single material for manufacturing all the components that form the valve was used, and for the relief valve 1 of the present invention, indicated by letter B, a first material was used for manufacturing the crank arm 3 and a second material, different to the first material, for manufacturing the shaft 4, with the connection between the crank arm 3 and the shaft 4 being carried out by means of a process of attrition welding.

[0046] Furthermore, the relief valve of the state of the art (letter A) tested in the fatigue resistance test is obtained by means of an investment casting process, whereas the relief valve 1 of the present invention (letter B) is obtained by means of forging and/or machining process, followed by a process of attrition welding, such as described previously.

[0047] As can be noted in the graphic representation of the fatigue resistance test, illustrated in FIG. 7, valve A of the state of the art presented a survival probability of 50% when applying a force slightly over 480 Newton (N). In contrast, valve B of the present invention shows a survival probability of 50% when a force over 650 Newton (N) was applied.

[0048] The increase of fatigue resistance for valve B of the present invention in relation to valve A of the state of the art is therefore proven.

[0049] Besides the different materials used for manufacturing the valve flap 2, of the crank arm 3 and of the shaft 4 of the relief valve 1 of the present invention and the use of the manufacturing process of forging/machining and welding, the present invention further provides the application with a coating on the outer surface of each of the components of the valve 1, said coating comprising a ceramic coating, PVD or CVD, or a nitriding hardening treatment.

[0050] Said coatings, jointly with the materials and processes used for obtaining the relief valve 1 of the present invention guarantee excellent resistance and durability not only to the valve per se, but to the turbocharger as a whole, since it achieves improved working and performance of the valve 1.

[0051] In short, the relief valve 1 of the present invention presents greater resistance in relation to the valves of the state of the art, due to the possibility of using different materials, specific for each component of the valve 1, being obtained by means of simpler processes and which present reduced costs in relation to the processes used in the state of the art.

[0052] Having described examples of preferred embodiments, it should be understood that the scope of the present invention encompasses other possible variations, being limited solely by the content of the accompanying claims, potential equivalents being included therein.