Patent Publication Number: US-9889501-B2

Title: Method for producing a turbocharger housing

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention: 
     From the prior art, it is known to produce turbocharger housings in a casting process. In this case, the construction of the casting mold is designed so that use is made of a separate oil core and water core which are located in an outer mold. 
     BRIEF SUMMARY OF THE INVENTION 
     It is the object of the present invention to provide an improved method for producing a housing, particularly a turbocharger housing or a part of a turbocharger housing. 
     This object is achieved by a method for producing a housing having the features of the claims. 
     According to this, a method for producing a casting, especially a housing of a turbocharger, is provided according to the invention, wherein at least one mold part, for forming the casting, has a parting plane in each case which is arranged at a predetermined angle to the longitudinal axis of the casting and wherein at least one core element is provided. 
     The method in this case has the advantage that the mold part can be reproduced in one mold half of a molding flask and the core element can be inserted in the one mold half. As a result, a casting can be produced with increased accuracy since the mold part is not split into two parts along its longitudinal axis and which are formed in each case in the two mold halves of a molding flask and then by assembly in the molding flask form the mold of the casting. 
     Instead of this, the mold of the casting, for example completely or for the most part completely, can be formed in one mold half of the molding flask, whereas only the feeders, for example for the most part, are arranged in the other mold half. 
     In addition, a method for producing a casting is provided, wherein at least one mold part and at least one first core element are provided, wherein the first core element forms at least one part of the external surface of the casting. 
     The method in this case has the advantage that the external surface can be produced with more complex structures or shapes since the core element subsequent to the casting can be destroyed, for example mechanically by vibrations, or the binding agent of the molding sand of the core element is destroyed by means of the heat during casting so that the core element disintegrates by itself. 
     Furthermore, a method for producing a casting is provided, wherein at least one mold part and at least two core elements are provided, wherein the two core elements can be located one inside the other and can be positioned in a mold half of a molding flask. 
     The method in this case has the advantage that as a result of this a casting can be manufactured with higher precision. In this case, the manufacturing tolerances can be reduced, in a process reliable manner, for example, to +/−0.5 mm. 
     Advantageous embodiments and developments of the invention can be gathered from the dependent claims and also from the description with reference to the drawings. 
     In one embodiment according to the invention, the casting is a housing of a turbocharger, for example a bearing housing or an impeller housing or a part of such a housing. 
     In a further embodiment according to the invention, the first core element is a water jacket core element. In this way, a corresponding turbocharger housing with cooling can be produced in a very simple manner, during which the cooling jacket is integrated into the housing or is formed in one piece with this. 
     According to a further embodiment according to the invention, provision is made for a second core element. The first core element and second core element can be located one inside the other in this case and can be positioned for example in a mold half of a molding flask. This has the advantage that a casting can be produced with higher precision. 
     In another embodiment according to the invention, the mold part has a parting plane which is arranged at a predetermined angle to the longitudinal axis of the casting, for example at an angle of essentially 90°, and wherein the mold part can be formed for example in one mold half of a molding flask. In this case, at least one core element can also have a parting plane which is arranged at a predetermined angle to the longitudinal axis of the casting, for example at an angle of essentially 90°. This has the advantage that the shape of the casting can be reproduced in one mold half, in contrast to castings which are of a split design along the longitudinal axis and therefore have to be formed in both mold halves of a molding flask. 
     In a further embodiment according to the invention, the second core element is an oil core element, for example. This has the advantage that an oil feed and oil drain can be integrated into the housing of the turbocharger for supplying bearings with lubricant. 
     In another embodiment, at least one core element, or both core elements, forms, or form, a part of the external geometry or external surface of the casting. This has the advantage that the external surface can be formed with more complex structures or shapes since the respective core element is destroyed for removal from the casting. 
     According to a further embodiment according to the invention, the construction of the mold part and of the core element, or core elements, is reproduced for the most part completely, or almost completely, in one mold half of a molding flask. As a result, a casting can be produced with higher precision, without the occurrence, moreover, of unsightly flashes in the region of the parting plane between top and bottom mold halves. 
     In a further embodiment according to the invention, the respective core element can be produced from molding sand and a suitable binding agent so that it can be easily destroyed again for removal. In principle, however, one core element, or a plurality of core elements, can be used, consisting of different materials, for example materials which either vaporize, melt or disintegrate in another way (e.g. polystyrol), or they are melted before the casting (e.g. wax, resins). 
    
    
     
       The invention is explained in more detail below based on the exemplary embodiments which are represented in the schematic figures of the drawings. In the drawings: 
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  shows a sectional view of a molding flask with an arrangement consisting of a blank and a core element according to the prior art, 
         FIG. 2  shows a sectional view of a molding flask with an arrangement consisting of a blank and two core elements according to the invention, 
         FIG. 3  shows a sectional view of a molding flask with an arrangement consisting of a blank and two core elements according to a further example of the invention, 
         FIG. 4  shows an exploded view of a blank, and also of a water jacket core and an oil chamber core for forming a bearing housing of a turbocharger according to the invention, 
         FIG. 5  shows a view of a drag side of a molding flask, wherein the blank and the water jacket core and oil chamber core according to  FIG. 3  are shown in the assembled state; and 
         FIG. 6  shows a view of a corresponding cope side of the molding flask. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     In all the figures, similar elements, or functionally similar elements, and devices—unless stated otherwise—have been provided with the same designations. 
     A molding flask  10  for producing a blank from a cast material is first of all shown in  FIG. 1 . The molding flask  10  is shown in this case in greatly simplified form. The representation of feeders for feeding the liquid casting material has been dispensed with in this case for reasons of clarity. Furthermore, no mold drafts have been drawn in. 
     The blank or the impression  12  of the blank in the molding flask  10  is split in the longitudinal direction. This means that a cope  14  and a drag  16  of the molding flask  10  have an impression  12  of a cylinder half in each case, wherein both flasks  14 ,  16  in the assembled state form the complete cylindrical impression  12  of the blank. 
     For forming the cavity of the blank, a corresponding cylindrical core element  18  consisting of molding sand is inserted into the drag  16  in this case, as is shown in  FIG. 1 . The core element  18 , subsequent to the casting process, after the cooling of the casting, is mechanically destroyed again, for example by vibrations, in order to thus remove it again from the finished casting. 
     However, there are, for example, core elements in which the binding agent of the molding sand is selected so that if possible it is destroyed by means of the heat which is created during the casting process and consequently the core element subsequently disintegrates by itself without it having to first be mechanically destroyed, as previously described. 
     Shown now in  FIG. 2  is an exemplary embodiment for the arrangement of a blank or its mold part (pattern) and its core elements  18  in a molding flask  10  according to the invention. In contrast to the prior art, the blank or its mold part is not longitudinally split in this case, instead of this, the blank or its mold part (pattern) is formed in the drag  16 , as is indicated in  FIG. 2  by the impression  12  of the mold part. In this case, the mold instead of being longitudinally split can be horizontally split or split in a plane perpendicular to the longitudinal axis  22  of the blank. In this case, a mold part of the blank can be formed in the drag  16  and a mold part of the blank can also be formed in the cope  14 , as is indicated in  FIG. 2  by a dashed line. 
     Furthermore, for forming the cavities of the casting two corresponding core elements  18  are used. The liquid casting material is introduced via a feeder  24 , or via a plurality of feeders, which for example are arranged in the cope  14 . 
     The view in  FIG. 2  is in this case greatly simplified and purely schematic. The shape of the core elements  18  and the impression  12  of the blank or of its mold part (pattern) are shown in a greatly simplified form and only by way of example. In this case, for example no mold drafts etc. have been shown. The same also applies for example to the shape, the arrangement and the number of feeders  24  for introducing the liquid casting material. Furthermore, the wall sections  26 ,  28  of the blank, which are shown in  FIG. 2 , are designed so that they are interconnected, which, however, is not shown in  FIG. 2 . The simplified view in  FIG. 2  serves purely for clarification of an example for the arrangement of a mold part and corresponding core elements  18 . The invention is not limited to this example. 
     In the example, as is shown in  FIG. 2 , the first core element  18  forms a first cavity of the subsequent casting. The second core element  18 , moreover, forms a second cavity of the subsequent casting. The outer wall  30  of the subsequent casting in this case is formed in the present example by the impression  12  of the mold part (pattern) in the drag  16 . 
     Shown now in  FIG. 3  is an exemplary embodiment for the arrangement of a blank or its mold part (pattern) and its core elements  18  in a molding flask  10  according to a further example of the invention. In this case, the impression  12  of the blank or of the mold part (pattern) is first of all formed in the molding flask  10  and then the blank or mold part is removed again. After this, a core element, or a plurality of core elements  18 , for example, can be selectively arranged or positioned in the impression  12  of the mold part. In the present case, the first core element  18  is designed in such a way in this case that it can be inserted into the impression  12  of the blank or its mold part in order to form the outer wall  30  of the subsequent casting. 
     Whereas the first core element  18  forms the outer wall  30  of the subsequent casting, the second core element  18  in turn forms the cavity of the subsequent casting and its inner wall. The second core element  18  in this case is correspondingly inserted into the first core element  18 , for example. The exemplary embodiment in  FIG. 3  is also shown in a schematic and greatly simplified form like the exemplary embodiment in  FIG. 2 . 
     Furthermore, an exploded view of a further exemplary embodiment of the invention is shown in  FIG. 4 . Shown in  FIG. 4  in this case, as core elements  18 , are the core elements  38 ,  40  for forming a bearing housing of a turbocharger. With this, provision is made for a blank or its mold part  20  (pattern) ( FIG. 4 ) which in the present example ( FIG. 4 ) is formed with an oil drain  36  and the water connection holes (of subsequent water jacket core element  38 ). 
     Furthermore, as core elements  18 , provision is made for a water jacket core element  38  and also an oil chamber core element  40  for forming a water jacket around the bearing housing in order to be able to subsequently additionally cool this during operation. Furthermore, the oil chamber core element  40  is provided in order to subsequently feed a lubricant to the bearings of the bearing housing. 
     In contrast to the prior art, as is shown in  FIG. 1 , the blank or its mold part  20  (pattern) is not split in the longitudinal direction or along its longitudinal axis. Instead of this, the new design according to the invention is based on a compact mold construction. In this case, the water jacket core element  38  and the oil chamber core element  40  form a partial contour, for example, of the external geometry of the housing in each case. The respective parting planes of the mold part  20 , of the water jacket core element  38  and of the oil chamber core element  40  of the bearing housing which is to be produced do not extend in this case as in the prior art in the longitudinal direction or along the longitudinal axis  42 , as is shown in an example in  FIG. 1 , but the parting planes extend for example essentially perpendicularly to the longitudinal axis  42  of the housing which is to be produced. The parting plane  44  of the oil chamber core element  40  is indicated in this case in  FIG. 4  by way of example by means of hatching. In principle, provision can also be made for at least one parting plane which is inclined by an angle which is more than or less than 90° relative the longitudinal axis  42 , depending upon function and intended use. 
     As a result of the more compact mold construction, as is shown in  FIG. 4 , for example, a more precise positioning of the internal geometry in relation to the external geometry of the housing can be achieved. Initial holding points (not shown) for the mechanical machining can also be positioned on the surfaces of the external geometry which are formed by the oil chamber core element  40  and the water jacket core element  38 . 
     Contingent upon the mold construction and core construction, a water cooled bearing housing, for example, can be geometrically completely produced by means of an oil chamber core element  40  and a water jacket core element  38 , and also by means of a mold half, in this case being the drag  16 . In other words, the mold of the casting which is to be produced is formed completely in the drag with the necessary core elements, as is comparably shown in the example in  FIG. 3 . In principle, it is also possible to form the mold of the casting which is to be produced both in the cope  14  and in the drag  16  inclusive of the necessary core elements, as is indicated by a dashed line in the example in  FIG. 2 . 
     As is shown in the perspective view in  FIG. 5 , the blank or its mold part (pattern) is first of all formed in the molding flask in order to form a corresponding impression  12 , and is then removed again. A core element, or a plurality of core elements  18 , for example, can be selectively inserted or positioned in the impression  12  of the blank or mold part (pattern). 
     The two core elements  18 , i.e. the water jacket core element  38  and the oil chamber core element  40 , in this case are located one inside the other, for example, (see also  FIG. 6 ) and positioned in the drag or in this case the impression  12  of the mold part (pattern) in the drag. For reasons of clarity, the drag has been omitted in this case. 
     In the present case, as is shown in  FIG. 5 , the oil chamber core element  40  is located in the water jacket core element  38  and positioned in the drag (not shown) or the impression  12  of the mold part  20  or of the blank in the drag. This enables a massive tolerance restriction, for example in a process-reliable manner, to +/−0.5 mm in relation to the reference surface. As a result of this higher precision of the described arrangement, an increased cross-sectional area in the water passage can be made possible in a given installation space on account of the small tolerance window for the wall thicknesses between two core elements  18 ,  38 ,  40  or between an inner contour and an outer contour. 
     This larger cross section brings about improved heat dissipation and also enables the process-reliable removal of casting residues in the water passage and oil chamber of smaller turbocharger housings, as are used in motor vehicles, for example, on account of the better accessibility. 
     Shown in  FIG. 6  is a perspective view from the direction of the cope side of the molding flask. The cope and drag have been omitted in this case also for reasons of clarity. From the greatly simplified and schematic view in  FIG. 6  it can be gathered that the core elements  18  are located one inside the other, i.e. the oil chamber core element  40  is arranged or located in the water jacket core element  38 . 
     Although the present invention was described above based on the preferred exemplary embodiments, it is not limited thereto, but can be modified in a wide variety of ways. The previously described embodiments, especially individual features thereof, can be combined with each other in this case. 
     According to the exemplary embodiment for producing a bearing housing it is also possible to produce a turbine housing or compressor housing, for example, in such a way. The turbine housing in this case can also be formed with a water jacket, for example, for cooling purposes. In principle, it is also possible in this case to provide a parting plane in the longitudinal direction in elements of the casting which is to be produced, as is shown by way of example in  FIG. 1 . 
     The core elements  18 ,  38 ,  40 , as are shown in the exemplary embodiments in  FIGS. 2 to 5 , can be produced for example from sand with a suitable binding agent, as was previously described with reference to the prior art in  FIG. 1 . However, other materials or material combinations can also be used for producing core elements  18 ,  38 ,  40 . 
     Furthermore, the number of core elements, their shape and arrangement, etc., and also the number of mold parts, their shape and arrangement, etc., can be optionally varied, depending upon the casting which is to be produced. The same also applies to the provision of an oil feed and/or oil drain, and also of water connection holes. This can be optionally designed and be provided or omitted depending upon requirement. For example, a turbocharger housing may be provided with, or even without, a cooling jacket, or a plurality of cooling jackets. 
     As casting material for the bearing housing, for example a steel casting alloy and iron casting alloy, and also their modifications, such as D5, Simo, 1.4848, 1.4849, etc., can be provided. These, however, are only examples of materials from which the housing can be produced. The invention is not limited to these materials.