Abstract:
A method for producing a cast/sheet-metal composite body, comprising the following steps: provide a casting mold ( 12 ), place at least one sheet-metal part ( 11 ) in the casting mold ( 12 ), produce a cast part ( 2 ) interconnected with the at least one sheet-metal part ( 11 ), and apply pressure to the at least one sheet-metal part ( 11 ) to form a hollow space ( 8 ).

Description:
The invention concerns a cast/sheet-metal composite body and a method for producing it. 
   BACKGROUND OF THE INVENTION 
   If passages for a cooling fluid are to be integrated in a housing made of metal casting, e.g., for an alternator, two methods for producing them are known. On the one hand, the housing can be produced using the sand-casting method with an appropriate core. This is expensive for series production in particular. On the other hand, the housing can be produced in two parts using the diecasting method—if the geometry allows this—whereby the two housing parts must then be interconnected in sealed fashion. This is expensive as well. 
   SUMMARY OF THE INVENTION 
   The invention is based on the object of creating a method for producing cast parts in which passages can be integrated as easily as possible. The essence of the invention lies in the creation of a cast/sheet-metal composite body, in which, after the cast part is produced, the integrated sheet-metal part is deformed in plastic fashion. The advantage of this is that fluid-sealed and pressure-sealed passages can be formed even in highly inaccessible regions of a complex cast part. 
   The sheet metal part is composed of two superimposed metal sheets. The advantage of this is that the hollow space formed is bordered only by metal sheets and not by the cast part itself. As a result of this, greater resistance to corrosion can be attained. 
   Additional features and details of the invention result from the description of three exemplary embodiments with reference to the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a first method step for producing a composite body according to an initial exemplary embodiment, 
       FIG. 2  shows a second method step for producing a composite body according to the first exemplary embodiment, 
       FIG. 3  shows a third method step for producing a composite body according to the first exemplary embodiment, 
       FIG. 4  shows a fourth method step for producing a composite body according to the first exemplary embodiment, 
       FIG. 5  shows a fifth method step for producing a composite body according to the first exemplary embodiment, 
       FIG. 6  shows a sixth method step for producing a composite body according to the first exemplary embodiment, 
       FIG. 7  shows a cross section of the composite body according to the first exemplary embodiment, 
       FIG. 8  shows a sheet-metal part for producing a composite body according to a second exemplary embodiment, 
       FIG. 9  shows a top view of the sheet-metal part according to the visual-direction arrows IX—IX in  FIG. 8 , 
       FIG. 10  shows a further method step for producing the composite body according to a second exemplary embodiment, 
       FIG. 11  shows a top view according to the visual-direction arrows XI—XI in  FIG. 10 , 
       FIG. 12  shows a further method step for producing the composite body according to the second exemplary embodiment, 
       FIG. 13  shows a cross-sectional illustration of the composite body according to the second exemplary embodiment, 
       FIG. 14  shows a cross-sectional illustration of the composite body according to a third exemplary embodiment, 
       FIG. 15  shows a top view of the sheet-metal part of the composite body according to the third exemplary embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A method for producing a cast/sheet-metal composite body  1  will be described hereinbelow within the scope of a first exemplary embodiment with reference to  FIGS. 1 through 7 . The first description refers to the finished composite body  1 , with reference to FIG.  7 . The composite body  1  comprises a cast part  2 . Said cast part includes two annular connecting bars  3  arranged side-by-side and bordering an upwardly open connection bore  4  in each case. The connecting bars  3  are interconnected via a base plate  5 . A sheet-metal plate  6  extending substantially parallel to the base plate  5  is located underneath said base plate, which said sheet-metal plate is embedded and fixed in the cast part  2  along its entire edge portion  7  in pressure-sealed fashion. A passage  8  is formed between the base plate  5  and the sheet-metal plate  6 , which said passage interconnects the two connection bores  4 , inside each of which a connection fitting  9  is fixed by means of press fit. A tube  10  for the supply or carrying away of cooling water is secured to each of the connection fittings  9 , which extend past the respective connecting bars  3 . 
   To produce the composite body  1 , a sheet-metal blank  11  formed as a sheet-metal part is placed in a diecasting mould  12  composed of a first half  13  and a second half  14 , as shown in FIG.  1 . The sheet-metal blank  11  comprises an upwardly projecting edge portion  7 . The cast part  2  is then created in the mould  12 , whereby the edge portion  7  is interconnected with the cast part  2  in sealed fashion. The sheet-metal plate  6  lies on the underside of the base plate  5 . The cast part  2  is then machined-down and deburred, as shown in FIG.  3 . After this, as shown in  FIG. 4 , the connection fittings  9  are inserted in the bores  4 , in which they are fixed by means of press fit. The cast part  2  is then placed in a pressure application mould  15  that is composed of a first half  16  and a second half  17 . The mould  15  comprises an interior space  18  that basically matches the exterior contour of the part shown in  FIG. 4. A  recess  19  designed in the shape of a passage is provided in the half  17 , adjacent to the exposed sheet-metal plate  6 . Sealing rings  20  are arranged on the bars  3  to pressure-seal the interior space  18  from the environment. The half  16  comprises two upwardly open connection passages  21 , by means of which the sheet-metal plate  6  is acted upon with pressure via compressed air or a pressurized fluid. As a result of the pressure application, the sheet-metal plate  6  is pressed into the recess  19  and deformed in plastic fashion until it takes on the shape shown in  FIGS. 6 and 7 . As a result of the plastic compression strain, the passage  8  is produced between the base plate  5  and the sheet-metal plate  6 , which said passage interconnects—in sealed fashion—the connection fitting  9  situated on the left with the connection fitting  9  situated on the right. In the step shown in  FIG. 6 , the composite body  1  is subjected to an air-tightness test using compressed air, whereby potential leaks are detected over time by means of a drop in pressure. 
   The method described above has numerous advantages. By using comparably simple diecasting moulds  12 , it is possible to produce cast/sheet-metal composite bodies  1  having inboard passages  8 . The fact that installation space can be spared overall is of central significance here. The moulds  12  do not require cores, which would have to be removed in expensive fashion. Production costs can be greatly reduced as a result. In particular, single-component housings can be combined with heat exchangers, and they can be interconnected even in the case of geometrically complex shapes. When heat exchangers are involved, a cooling fluid is conducted through the passages  8 , so that the heat given off at the composite body  1  can be dissipated particularly efficiently, since the thermal conduction paths to the cooling system are shortened. Moreover, by using sheet-metal parts, the thickness of the passage walls can be reduced—at least on one side—in comparison with a wall consisting of cast material. Further installation space is spared as a result. 
   A second exemplary embodiment of the invention is described hereinbelow with reference to  FIGS. 8 through 13 . Identical parts are assigned the same reference numerals as in the first exemplary embodiment, the description of which is herewith referred to. Parts that are functionally identical but different in terms of design are assigned the same reference numerals plus one superscript mark. As in the first exemplary embodiment, the finished composite body  1 ′ is described initially with reference to FIG.  13 . The method for producing the composite body  1 ′ is then explained with reference to  FIGS. 8 through 12 . The composite body  1 ′ is a collector-ring end shield for an electrical alternator. It comprises an annular-cylindrical housing wall  22  having a center longitudinal axis  23  and a base  24  extending at a right angle to the center longitudinal axis  23 . A roller-bearing seat  25  for housing a rotor shaft is arranged in the center of the base. An axially projecting annular frame  26 —which is concentric with said roller-bearing seat and has a larger diameter—is interconnected with the base  24 , which said annular frame radially borders a fan wheel space  27  in the direction toward the center longitudinal axis  23 . An annular winding head space  28  for a winding head of the stator of the alternator is located between the annular frame  26  and the housing wall  22 . Distributed around the circumference, bores for clamping bolts are provided on the outside of the housing wall  22  extending parallel to the center longitudinal axis  23  to interconnect the two end shields of the alternator. A plurality of fan recesses  30  is provided in the base  24 , between the external circumference of the roller-bearing seat  25  and the annular frame  26 , which said fan recesses connect the fan wheel space  27  with the environment. A heat exchanger  31  is provided in the housing wall  22  and in the base  24 . Said heat exchanger is composed of an annular passage section  32  that is arranged circumferentially on the inside of the wall  22 , as well as a U-shaped passage section  33  interconnected with the passage section  32 , which said U-shaped passage section encloses the roller-bearing seat  25  while forming a keyhole opening  34 . The passage sections  32  and  33  are bordered by an internal metal sheet  35  and an external metal sheet  36  that are superimposed along their edges and are friction-welded to each other along one edge portion  7 ′. The metal sheets  35  and  36  are positioned, in pressure-sealed fashion, in the unit—comprising wall  22  and base  24 —developed as cast part  2 ′ along the edge portion  7 ′, and they are fixed there. In the region of the lower end of the passage section  32 , the exterior metal sheet  36  has two radially outwardly extending connection openings  37  that are connected via a connection passage  38  arranged on the wall  22  with a connection fitting  9  extending parallel to the center longitudinal axis  23 , which said connection fitting is fixed in a connection bore  4  with press fit. One of the two connection fittings  9  serves to supply cooling water, and the other serves to carry cooling water away. 
   The chronological sequence of the production method of the composite body  1 ′ is described hereinbelow with reference to  FIGS. 8 through 12 . A sheet-metal blank  11 ′ developed as sheet-metal part and having the structure shown in  FIGS. 8 and 9  is first produced. The sheet-metal blank  11 ′ has a ring portion  39  and a base portion  40 , whereby the base portion  40  basically comprises a U-shaped cross section, and the two arms of the U are developed integral with the ring portion  39  at their upper ends. The sheet-metal blank  11 ′ is composed of two superimposed metal sheets, i.e., the interior metal sheet  35  and the exterior metal sheet  36 , which are friction-welded to each other along the edge portions  7 ′. The sheet-metal blank  11 ′ is placed in a diecasting mould and covered with a cast part  2 ′ applied by injection moulding. The result is shown in  FIGS. 10 and 11 . In the next step, deburring and machining-down takes place, and the connection fittings  9  are inserted. Following this, the cast part  2 ′ is placed in a pressure-application mould  15 ′ in which recesses  19 ′ are provided adjacent to the exposed metal sheets  35  and  36 . The space between the metal sheets  35  and  36  is then acted upon with compressed air, so that the interconnected passage sections  32  and  33  are produced. The finished composite body  1 ′, shown in  FIG. 13 , is then subjected to an air-tightness test. 
   Due to the combination of diecast and sheet-metal parts, a heat exchanger  31 —in the case of the composite body  1 —can be positioned in the end shield of an alternator, so that the waste heat produced can be dissipated without a problem, even in the case of increased-output alternators. The total device is extremely space-saving. The coolant passage  8 ′ composed of the passage sections  32  and  33  is bordered only by the metal sheets  35  and  36 , but not by the cast material. Aluminum is often used as the material for the metal sheets  35  and  36 . Due to its degree of purity, aluminum is much more resistant to corrosion in the presence of fluids than the alloy used for the metal cast. 
   A third exemplary embodiment of the invention is described hereinbelow with reference to  FIGS. 14 and 15 . Identical parts are assigned the same reference numerals as in the first exemplary embodiment. Parts that are functionally identical but different in terms of design are assigned the same reference numerals plus two superscript marks. The composite body  1 ″ represents an annular-cylindrical housing wall  22 ″ in which a heat exchanger  31 ″ is integrated. The composite body  1 ″ has an annular-cylindrical housing wall  22 ″ in which a sheet-metal blank  1 ″ is integrated that is interconnected with the cast part  2 ″ along the edge portions  7 ″. A passage  8 ″ is produced between the cast part  2 ″ and the sheet-metal blank  11 ″ by means of the pressure application. Said passage is indicated in  FIG. 14  by a dashed line. The sheet-metal blank  11 ″ is developed as a strip meandering in shape that comprises recesses  41  open to the left and to the right in alternating fashion. Meander strips  42  are interconnected over metal bands  43  in the region of the recesses  41 . The meander strips  42  have an edge portion  7 ″ designed in the shape of a bar. Space is created, by means of the recesses  41 , for the axially extending clamping bolts housed in the bores  29 .