Abstract:
An engine block of a diesel engine cast integrally with the cylinder head, with a number of cylinders in line, including an outer wall ( 21 ) and a cylinder wall ( 13 ) for each cylinder with a first cooling space ( 22 ) for a liquid cooling medium and with a second cooling space ( 25 ) on top of a cylinder ceiling ( 14 ) with openings ( 15,16 ) for gas exchange valves, the first cooling space ( 22 ) enclosing all the cylinder walls ( 13 ) entirely. In order to strengthen and cooling the vulnerable zone at the transition from cylinder wall ( 13 ) to cylinder ceiling ( 14 ) the first cooling space of adjacent cylinders forms a gap ( 23 ) with a width ( 35 ) constant or increasing from top to bottom.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to an engine block of a diesel engine cast integrally with the cylinder head, with a number of cylinders in line, including an outer wall and a cylinder wall for each cylinder with a first cooling space for a liquid cooling medium between them and with a second cooling space on top of a cylinder ceiling with openings for gas exchange valves, the first cooling space enclosing all the cylinders entirely and extending upwards beyond the cylinder ceiling. 
         [0002]    This design is also known as “Monoblock”. It avoids the drawbacks of the design with a separate cylinder head: The bolts joining the cylinder head to the engine block, and the gasket between them. It is therefore particularly suitable for Diesel engines of high performance. The high performance entails high pressures and needs intensive cooling by the liquid cooling medium, in particular around the cylinder ceilings. However, this design is demanding for the casting shop. 
         [0003]    Such an engine is known from DE 19 38 134, for instance. Its cylinder walls are circumflown by a cooling liquid (usually water). In order to provide sufficient rigidity to the surrounding of the cylinder ceilings, these are incorporated in a through horizontal wall. But this divides the two cooling spaces, the cylinder walls are structurally vulnerable and not directly circumflown by the cooling liquid. 
         [0004]    The German Utility Model 1 995 270 also discloses an engine in monoblock design, wherein the cylinder ceilings are united in a through plate. The cooling space enclosing the cylinder walls therefore does not reach beyond the cylinder ceilings all around. The sensible transition zone between cylinder walls and cylinder ceilings thus is not circumflown by the cooling water. 
         [0005]    The Austrian Patent 382 429 discloses a further generic engine, including injection units in the cylinder head supplied with fuel by a common rail and with a first cooling space that rises beyond the cylinder ceilings, but without overlapping them. As can be seen, the cooling water passes from the first cooling space to the second cooling space (in the cylinder head) through a horizontal bore drilled from outside and blocked. This cannot provide a cooling water flow to the upper cooling space sufficient for a high performance engine. 
         [0006]    The JP 07-071310 relates to a further engine in monoblock design. According to  FIG. 3 , the first cooling space overlaps the cylinder ceiling in the region of the valves, but only slightly. In order to  achieve the desired improvement of structural strength and of cooling, overlap must coincide with the width of the gaps between adjacent cylinders around the cylinder walls which increases from top to bottom. 
         [0007]    DE 100 33 271 B4 relates to the casting core for the cooling jacket of an engine of conventional design, not monoblock. In this design the problem of the transition between cylinder wall and cylinder ceiling does not arise. The described casting process uses inserts, but inserted into the core. This is time consuming, limiting the design and the insert must be destroyed when unmolding the cast part. 
         [0008]    When preparing the casting mould for such an engine block, the core parts corresponding to the cooling space around the cylinder wall must be made with a draft angle of some degrees of angle. This is necessary in order to enable the core parts to be extracted from the core mould (also called core box) without being damaged. This draft angle is always featured, even if not visible in conventional drawings because it is only of some degrees of angle. It is of particular importance with very thin core parts corresponding to the regions of the water space between adjacent cylinders. Thin core parts are very fragile. 
         [0009]    The draft angle of the core part for this region entails that it is wider near the cylinder  ceiling than at its lower end. This has the consequence that the wall thickness of the cylinder wall is smaller on top, in the particularly vulnerable transitional region between cylinder wall and cylinder ceiling. This vulnerable region limits the specific performance of an engine. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention sets out to eliminate this vulnerability. According to the invention the cooling space between the cylinder walls of adjacent cylinders has a gap with a width constant or increasing from top to bottom. Top and bottom relates, as in the following, to an vertically set engine with the cylinder ceiling on top and the crankshaft at the bottom. Likewise horizontal and vertical. 
         [0011]    This measure has the effect that the cylinder wall is not impaired or (if the width of the gap increases towards the bottom or if the gap is bridged) even strengthened and that the transitional region is intensely cooled. This allows a further increase of the specific performance. 
         [0012]    Preferably the first cooling space overlaps the cylinder ceiling at least in the region of the exhaust valves. The overlap entails a further increase of the cooling of the vulnerable zone, particularly advantageous in the region of the exhaust valves.  
         [0013]    When the engine block includes wall parts separating the first cooling space from the second cooling space, an advantageous embodiment comprises two horizontal bores, one drilled from one outer wall, the other drilled from the opposite outer wall, and one of them ending in the region of the fuel injector. This enables the cooling liquid rising from the first cooling space to form a jet directed towards the injector and so provides effective cooling of the sensitive injector. With two such horizontal bores arranged in pairs per cylinder, the second cooling space is fully integrated in the circulation of the cooling fluid. 
         [0014]    From the manufacturing point of view, drilling these bores from outside is very easy, considering that the engine block undergoes machining at various locations after casting. The opening of the bores in the outer wall is easily plugged in the same way as other core positioning bores. 
         [0015]    The invention also consists in a casting method particularly suitable for providing for the gap between adjacent cylinders according to the invention. This, assuming that the parts of the core are formed separately from suitably prepared sand in core moulds and that the core part corresponding to the gap between adjacent cylinders is formed by means of separate inserts in each core mould, the shape of  which corresponds to the width of the gap or the variable width of the gap, as the case may be. 
         [0016]    According to the invention the insert of constant or diminishing width is slid into the core mould for shaping the core (the core box) in vertical direction. To this end vertical guideways are provided in the core mould and on the insert. When the core is taken out of the core mould, the insert is lifted out together with the core part—therefore the guideways—and the insert is removed sideways. Thus, only one simple additional core tool is required. The insert consists of a durable material and therefore can be used again. Further, the side of the insert opposite the guideways can have a freely determined shape. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    In the following, the invention will be described and commented along with the following drawings: 
           [0018]      FIG. 1 : A longitudinal section of a generic engine according to the state of the art, 
           [0019]      FIG. 2 : A longitudinal section of a part of an engine according to the invention, 
           [0020]      FIG. 3 : A cross section of the engine of  FIG. 2  along in  FIG. 5 , 
           [0021]      FIG. 4 : A cross section of the engine of  FIG. 2  along IV-IV in  FIG. 5 , 
           [0022]      FIG. 5 : A horizontal section of the engine of  FIG. 2  along V-V in  FIGS. 3 ,  
           [0023]      FIG. 6 : A cross section through the mould for casting the engine block of  FIG. 2 , 
           [0024]      FIG. 7 : A core mould for making a core part for the casting mould according to the inventive method. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Referring to  FIG. 1 , the problem the invention sets out to solve will be explained with regard to the state of the art. The engine block  1  with a number of cylinders in line is cast integrally with the cylinder head part  2 . The cylinder walls  3  enclose the combustion space  5  and are enclosed by cooling spaces and circulated around by a cooling liquid (normally water). In the casting mould, the cooling spaces are materialized by sand core parts. These are formed in special core moulds. In order to withdraw the core parts from the core mould without damage, a draft angle of some degrees must be implemented; all the more the thinner and more fragile the core parts are. The core is particularly thin in the gap  6  between the cylinder walls  3  of adjacent cylinders. Due to the draft angle, the width of the gap  6  increases from below up to the cylinder ceiling  4  and the wall thickness of the cylinder walls therefore decreases. By this, the cylinder walls  3  are thinnest in the transition to the cylinder ceiling  4 , the region of highest mechanical and thermic strain. This weakness limits the specific power of the engine, lest cracks would occur in this region.  
         [0026]      FIG. 2  shows the engine block according to the invention in longitudinal section, the section being only through part of an engine of, for example,  6  cylinders. The engine block  10  comprises a cylinder part  11  and an integral head part  12 . Each cylinder comprises a cylinder wall  13  and a cylinder ceiling  14  with an opening  15  for a suction valve, an opening  16  for an exhaust valve and an opening for an injector  17  ( FIG. 3 ). An inlet channel  31  leads to opening  15  and an exhaust channel  32  ( FIG. 4 ) starts from opening  16 . 
         [0027]      FIG. 3  is a first cross section of the engine block. Cylinder wall  13  and cylinder ceiling  14  enclose a combustion space  18  each. Each cylinder wall is enclosed by a first cooling space  22 . It is common to all cylinders and its outer enclosure is an outer wall of the engine block  10 . The first cooling space extends from the lower region of the engine block  10  upwards and ends higher than the outer surface of the cylinder ceiling  14  at  29 . The first cooling space  22  forms a gap  23  (see  FIG. 2 ) between adjacent cylinders. The width  35  of this gap  23  according to the invention is constant or decreases from bottom to top or even has a special contour. There could be a bridge between adjacent cylinders, for example. This gap  23  extends upwards beyond the cylinder ceiling  14  and ends in an extension  24  overlapping and partly embracing the cylinder ceiling  14 . By this, the thickness of the cylinder wall  13  in the vulnerable  region ( 8  in  FIG. 1 ) is not reduced or even increased and the transition to the cylinder ceiling  14  is circumflown. 
         [0028]    The cylinder head part  12  includes a second cooling space  25  separated from the first cooling space  22  by a partition wall  26 . The partition wall  26  is of crumbled shape and, taking part in the in the formation of inlet channel  31 , exhaust channel  32  and the opening for the injector  17 , has also vertical regions. Between these, the partition wall  26  extends downwards until the outer surface of the cylinder ceiling  14  with which it merges. The second cooling space  25  thus ends lower than the top region  29  of the first cooling space  22 . In order to connect the second cooling space  25  with the first cooling space  22 , merely a first horizontal transverse bore needs to be drilled in the readily cast engine block and closed by a plug  28  at its outer end. 
         [0029]      FIG. 4  shows a second section across the engine block  10  in a different parallel plane. This section runs across the opening  16  for the exhaust valve. Here, it is clearly visible that the first cooling space  22  very substantially overlaps the cylinder ceiling  14  in the region of the exhaust valve, at  30 . A second transverse bore  33  can be seen here on the other longitudinal side  21 ′ of the engine block, also connecting the first cooling space  22  with the second cooling space  25 . Its outer end is closed  by a ball  34 . The second transverse bore  33  is directed towards the injector  17 , cooling this sensitive organ as well. 
         [0030]    Horizontal section of  FIG. 5  is in a plane through the center lines of the transverse bores  27 ,  33 . It intersects the partition wall  26  separating the two cooling spaces ( 22 ,  25 ), and also the outer walls  21 , see the hatched patches. It shows the first cooling space  22  between the outer walls  21  and the cylinder walls  13  of the individual cylinders and the gap  23  between adjacent cylinders. The core, mentioned below, corresponds to the first cooling space  22 . The core includes core parts in and around this gap  23 , of particular concern. The situation would be similar with an engine with four valves per cylinder. 
         [0031]      FIG. 6  shows the casting mould for casting an engine block according to the invention, summarily indicated with  40 , as an introduction to the description of the casting method according to the invention. In a two-part core box (OK and UK), indicated only by the separation line  41 , core parts—not shown in detail—are inserted. The core parts correspond to the hollows of the cast piece (for example core part  22 * to the first cooling space  22 , and so on). Essential for the invention is core part  22 * for the first cooling space  22 . Further core parts are core part  25 * for the second cooling space  25  and the core parts corresponding to the channels  31 ,  32 .  
         [0032]      FIG. 7  depicts the forming tool essential for the casting process according to the invention. Its purpose is the making of the core part  22 * and it is summarily indicated with  50 . The inner contour of the outer walls  56  of the forming tool corresponds to the inner contour of the outer wall  21  of the engine block and the towers  51  correspond to the outer contour of cylinder wall  13  and cylinder ceiling  14 . Each of the towers  51  has a vertical (thus not inclined by the draft angle) dovetail groove  52  for an insert  53  which is shifted (arrow  57 ) into the grooves in vertical direction as part of the forming tool for making the core part 
         [0033]    The insert  53  has a front surface  55  with a generatrix that is also vertical or even of arbitrary shape. In the latter case, the shape of the front surface can have particular features (for example also crevasses corresponding to a bridge between adjacent cylinders, not shown). The front surface  55  corresponds to the shape of core part  42  in the gap  23  between adjacent cylinders. As next step, the core part is built by insufflating core sand into the core mould  50 . The so shaped core part  42  is extracted along the dovetail grooves  54  from the core mould together with the insert  53 . This is enabled by the vertical guidance provided by the grooves  54 . As next step, the inserts  53  are separated from the core part  42  in horizontal direction and core part  22 * is ready for fitting in the mold, with the contour of the gap  23  according to the invention.