Abstract:
In a method for casting a cylinder head of a piston engine in a region of cooling channels for valve seat rings, a separate core is provided for defining cooling channels, and the cooling channel core is mounted in a bottom plate of a casting mold at various points thereof. The cooling channels for the valve seat rings have a cooling channel region formed by two interconnected rings and at least one cooling fluid supply channel and at least one cooling fluid drain channel. The two rings are disposed at a distance from the valve seat rings, adjacent to them.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority, under 35 U.S.C. §119, of German application DE 10 2007 030 482.1, filed Jun. 30, 2007; the prior application is herewith incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention concerns a method for casting a cylinder head of a piston engine in the region of cooling channels for valve seat rings, wherein a separate core is provided for the cooling channels, and the cooling channel core is mounted in a bottom plate at various points of the bottom plate of a casting mold. Moreover, the invention concerns cooling channels for valve seat rings of a cylinder head of a piston engine, especially cooling channels made according to the invention. 
         [0003]    A method for the casting of a cylinder head of a piston engine in the region of cooling channels for valves is known from published, European patent application EP 1 239 135 A2 (corresponding to U.S. patent publication No. 2002/0124815), wherein a separate core is provided for the cooling channels, and the cooling channel core is mounted in a bottom plate at various points of the bottom plate of a casting mold. The cooling channels produced by this method serve, in particular, for improved cooling of the cylinder head in the region of the combustion chamber. The cooling channels are also positioned in the region of two intake valves, two exhaust valves, and one fuel injection nozzle. A feed channel for cooling fluid is connected to a middle cooling channel, which is positioned next to the two exhaust valves between them and the injection nozzle. One end of the middle channel is connected to a drain channel at a crankcase end. The other end of the middle cooling channel emerges into two cooling channels, one of these cooling channels being arranged at the side of the exhaust valve arrangement away from the middle cooling channel and the other cooling channel at the side of the arrangement of the two intake valves away from the middle cooling channel. The outer cooling channels likewise communicate with the drain channels at the crankcase end. Thus, the three cooling channels form a kind of double U arrangement, where the two U-shapes share a leg in common. 
         [0004]    The core for the casting of the cooling channels is fashioned in accordance with this arrangement of the cooling channels, so that the core has channels for the passage of the cooling fluid. 
         [0005]    European patent EP 0 206 125 B1 describes a cylinder head of a fluid-cooled internal combustion engine, in which a valve ring channel is arranged around each intake and exhaust valve, fully enclosing the valve and emerging into a respective cooling channel. 
         [0006]    German patent DE 34 12 052 C2, corresponding to U.S. Pat. No. 4,593,655, describes a cooling device with forced flushing for the cylinder head of an internal combustion engine, in which each valve has a valve seat ring, surrounded by an annular channel, in which a coolant circulates during the operation of the internal combustion engine. The valve seat ring forms part of the wall of the annular channel, so that the coolant comes into direct contact with the valve seat ring. The problem with this arrangement is the sealing off of the valve seat ring from the combustion chamber and from the intake and exhaust channel. 
         [0007]    Published, European patent EP 1 329 628 A2 describes a cylinder head with a cooling channel system for a piston engine, especially a large Diesel engine, configured as a two-stroke Diesel engine and having no intake valve. The cylinder head has cooling channels around the respective exhaust valve, one of the cooling channels being arranged concentric to the exhaust valve. 
       SUMMARY OF THE INVENTION 
       [0008]    It is accordingly an object of the invention to provide a method for making cooling channels in the cylinder head of an internal combustion engine which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, which provides an economical production method for cooling channels to cool the valve seat rings in a cylinder head of a piston engine, as well as to indicate a configuration of these cooling channels ensuring an effective cooling of the seat rings of the intake and/or exhaust valves. 
         [0009]    The invention proposes a method for the casting of a cylinder head of a piston engine in the region of cooling channels for valve seat rings. A separate core is provided for the cooling channels, and the cooling channel core is mounted in a bottom plate at various points of the bottom plate of a casting mold. A separate cylinder head water core is mounted in the bottom plate and/or the cooling channel core, such that the cooling channel core is disposed between the bottom plate and the cylinder head water core. An intake channel core and/or an exhaust channel core is mounted in the bottom plate, such that two separate core regions of the channel core pass through at least one passage in the cylinder head water core and regions of the cooling channel core, which have two rings. 
         [0010]    Thus, the method of the invention occurs in the sequence of the mounting of the cooling channel core, the mounting of the separate cylinder head water core, and the mounting of the intake channel core and/or the exhaust channel core. What is important here is that the cooling channel core is disposed between the bottom plate and the cylinder head water core. The cooling channel core, the cylinder head water core, and the intake channel core or exhaust channel core can be made outside the casting mold and be preassembled there, for example, by gluing or screw fasteners, and then be placed together into the casting mold. Thanks to this configuration and mounting of the cooling channel core, it is possible to create cooling channels enclosing the valve seat rings and integrated in the region of the flow of cooling fluid to the crankcase. The cooling channel core is a sand core, for example, between the actual cylinder head water core and a chill mold bottom plate. In this way, it is possible to preassemble the actual cylinder head water core and the cooling channel core as sand cores outside the chill mold and install them together into the chill mold. By proper configuration of the cooling channel core, it is possible to integrate the injector borehole, through which the cooling fluid enters the cooling channels and heretofore produced by mechanical drilling, into the cast cooling channels for the valve seat rings, thus producing it by casting. This provides substantial cost potentials. 
         [0011]    Thanks to the method of the invention, cooling channels can be made for valve seat rings, and these cooling channels are not in contact with the valve seat rings, but rather a casting wall of any desired thickness is left in place. Thus, there are no problems with sealing off between the cooling channels and the valve seat rings. 
         [0012]    The separate core regions of the intake channel core and the exhaust channel core are now preferably mounted in valve seat projections of the bottom plate or in valve seat cores, which are mounted in the bottom plate. 
         [0013]    The invention furthermore proposes cooling channels for valve seat rings of a cylinder head of a piston engine, especially cooling channels made according to the above-described method. The cooling channels have a cooling channel region formed by two interconnected rings, with at least one cooling fluid supply channel connected to the cooling channel region and at least one cooling fluid drain channel connected to the cooling channel region. The two rings are disposed at a distance from the valve seat rings, adjacent to them. The particular ring surrounds an intake or exhaust channel of the cylinder head. 
         [0014]    Thus, according to the invention, the two rings surround the intake or exhaust channels of the cylinder head. The two rings surround either two exhaust valves or two intake valves. It is also conceivable to provide four rings, two rings surrounding two intake valves and two rings surrounding two exhaust valves. The cooling channels are disposed at a distance from the valve seat rings, but in any case adjacent to them. Thus, cooling fluid does not get into contact with the valve seat rings. Thanks to the close arrangement of the rings relative to the valve seat rings, an effective and homogeneous dissipation of heat from the valves and the valve seat rings is achieved, bringing about a homogeneous surface temperature in the combustion space and contributing substantially to lowering the temperature in the cylinder head. 
         [0015]    Preferably, the cooling channels are connected to one common supply channel and several drain channels. 
         [0016]    The flow through the cooling channels is constrained, in particular, by a supply channel known as the injector supply channel, the injector supply channel being fed from the drain side via a pressure head. High flow velocities, around 4 to 6 m/s, are adjusted in the injector supply channel. This impulse makes possible a flow into the rings. At the same time, the injector supply channel brings about an optimal cooling of the hot spots upstream from a fuel injection nozzle of the cylinder head in the direction of the exhaust valve or exhaust seat rings when the cooling channels surround the exhaust channels of the cylinder head. Thanks to this combination of injector cooling of the injection nozzle and good head dissipation in the region of the seat ring, the cylinder head is cooled optimally and homogeneously in the combustion space. 
         [0017]    In accordance with an added feature of the invention, the cooling fluid supply channel can be brought to communicate with a supply channel for cooling fluid at a crankcase side. 
         [0018]    In accordance with an additional feature of the invention, the two interconnected rings have a shared straight annular segment, with which the cooling fluid supply channel is connected. Each of the two interconnected rings has a respective annular segment being circular in shape. The respective annular segment has two ends connected to the shared straight annular segment. 
         [0019]    In accordance with a further feature of the invention, the drain channel is one of a plurality of drain channels, and each of the two interconnected rings empties into one of the drain channels in a region away from the shared straight annular segment. Preferably, one of the drain channels is a drain channel situated adjacent to a spark plug or an injection nozzle. 
         [0020]    In accordance with another feature of the invention, a respective one of the drain channels can be brought into communication with a further drainage channel for the cooling fluid at the crankcase side. 
         [0021]    In accordance with another added feature of the invention, a further cooling channel region is formed in a region of a flow end of the straight annular segment and empties into one of the drain channels. The one of the drain channels communicates with a cooling channel of the cylinder head, and the cooling channel of the cylinder head serves for actual cooling of the cylinder head. The cooling fluid supply channel and at least one of the drain channels are in direct communication with the cooling channel for the cooling of the cylinder head. 
         [0022]    In accordance with another further feature of the invention, the annular segments are disposed concentric to an axis of rotation of the valve seat ring facing the two interconnected rings. 
         [0023]    In accordance with a further additional feature of the invention, the two interconnected rings surround two exhaust valve seat rings. 
         [0024]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0025]    Although the invention is illustrated and described herein as embodied in a method for making cooling channels in the cylinder head of an internal combustion engine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0026]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING 
         [0027]      FIG. 1  is a diagrammatic, exploded perspective view of partial regions of a casting mold with a bottom plate, a cooling channel core, a cylinder head water core, an intake channel core and an exhaust channel core according to the invention; 
           [0028]      FIG. 2  is a diagrammatic, exploded perspective view of the bottom plate and the cooling channel core shown in  FIG. 1 ; 
           [0029]      FIG. 3  is an exploded, side view of the parts shown in  FIG. 1 , illustrating the assembly sequence of the parts; 
           [0030]      FIG. 4  is a diagrammatic, three-dimensional view of the parts shown in  FIG. 1 , in their assembled condition; 
           [0031]      FIG. 5  is a diagrammatic, three-dimensional view from underneath of the cooling channel core, the cylinder head water core, the intake channel core and the exhaust channel core. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    Referring now to the figures of the drawing in detail and first, particularly, to  FIG. 1  thereof, there is shown a region of a chill mold necessary to understand the invention. One notices a chill mold bottom plate  1  with level surface region  2 , which after the casting process represents the flat bottom side of the cylinder head in the region of a cylinder, also with an elevated region  3  as compared to the flat surface region  2 , which represents the combustion space of the cylinder when the cylinder head is finished, and finally four annular segments  4  and  5  projecting beyond the elevated region  3 . The annular segments  4  and  5  form recesses in the cylinder head when it is cast and finished, serving to accommodate the valve seat rings in the final machined cylinder head. The annular segments  4  pertain to the two intake valves of the cylinder, and the annular segments  5  to the two exhaust valves of this cylinder. 
         [0033]    The two annular segments  4  form a pair of annular segments  6 , the two annular segments  5  a pair of annular segments  7 . The respective annular segment pair  6  or  7  is disposed at an inclination relative to the flat surface region  2  by the respective valve angle; this inclination is dictated by the camber of the elevated region  3 , and the inclination of the annular segment pairs  6  and  7  corresponds to the tilt of the valves. 
         [0034]    The bottom plate  1  has bearing depressions  8  and  9  in the flat surface region  2 , in opposite end regions of the bottom plate  1 . The arrangement shown in  FIG. 1  is symmetrical to a plane running perpendicular to the surface region  2  and passing through the bearing depressions  8  and  9 . In the region of the other two sides of the bottom plate  1 , it is provided with two bearing depressions  10  and  11  in the flat surface region  2 , adjacent to the annular segment pair  7  and the elevated region  3 , whose cross section, cut parallel to the flat surface region  2 , is identical to but considerably smaller than the cross section of the bearing depressions  8  and  9 . 
         [0035]    As is especially visible in the representation of  FIG. 2 , the bearing depressions  9 ,  10  and  11  serve to bear a cooling water core  12  in the bottom plate  1 . The cooling water core  12  is configured as a sand core. It has two interconnected rings  13  and  14 , the ring  13  having a circular annular segment  15  and the ring  14  a circular annular segment  16  and both rings  13  and  14  possessing a common straight annular segment  17 , which joins the ends of the annular segments  15  and  16 . 
         [0036]    The cooling water core  12  has a straight web  18  as a prolongation of the straight annular segment  17 , whose end away from the annular segment  17  is connected to a block like bearing element  19 , which is shaped complementary to the bearing depression  9 . At the end away from the straight annular segment  17 , the annular segment  15  is joined to a web  20 , whose end away from the annular segment  15  is joined to a bearing element  21 , which is shaped complementary to the bearing depression  10 . Accordingly, the other annular segment  16  in its region away from the straight annular segment  17  is joined by a web  22  to a bearing element  23 , which is shaped complementary to the bearing depression  11 . 
         [0037]    The bearing elements  19 ,  21  and  23  are provided, in their upper region, with seats  24  for inserting a separate cylinder head water core  25  onto the cooling water core  12 . The cylinder head water core  25  has core projections  26 ,  27  and  28  for this purpose, with corresponding recesses for the seats  24 . In the region of the end away from the core projection  26 , the cylinder head water core  25  is provided with another core projection  29 , which is provided with a cross sectional shape complementary to the bearing depression  8 . 
         [0038]    The assembly of cooling water core  12  and cylinder head water core  25  can take place separately or in the process of the preassembly outside of the chill mold. During the assembly, one first inserts the cooling water core  12  in the sense of the method step per arrow  1  in  FIG. 3  with its bearing elements  19 ,  21  and  23  into the bearing depressions  9 ,  10 , and  11  of the bottom plate  1 . Next, according to the step per arrow  2  in  FIG. 3 , the cylinder head water core  25  is placed by its core projections  26 ,  27  and  28  onto the seats  24  of the bearing elements  19 ,  21  and  23  of the cooling water core  12 , on the one hand, and on the other hand the cylinder hear water core  25  is inserted by its core projection  29  into the bearing depression  8  of the bottom plate  1 . As can be seen from  FIG. 4 , the annular segments  15  and  16  of the cooling water core  12  enclose the annular segments  5  concentrically and the straight annular segment  17  is disposed between the two annular segments  5 . Thanks to the described arrangement, the cooling water core  12  is arranged between the bottom plate  1  and the cylinder head water core  25 . 
         [0039]    Adjacent to the annular segments  4  and adjacent to the annular segments  5 , the cylinder head water core  25  is provided with openings, which in the assembled condition pass through two core channels  31  of the intake channel core  32  and exhaust channel core  33 . In the region of the exhaust channel core  33 , two openings  30  are provided, whereby each opening  30  accommodates one core channel  31 . In the region of the intake channel core  32 , the cylinder head water core  25  is provided with only one opening  30  (see  FIG. 5 ). 
         [0040]    After the cylinder head water core  25  has been mounted, the intake channel core  32  and the exhaust channel core  33  are mounted. In the specific sample embodiment, as can be seen from  FIG. 3 , first the exhaust channel core is mounted per arrow  3  and then the intake channel core  32 , as shown by arrow  4 . 
         [0041]    The mounting of the particular channel core  32  and  33  is done by inserting it with its core channels  31  through the opening  30  or the two openings  30 , respectively, and in the region of projecting cylindrical shoulders  34  the annular segments  4  and annular segments  5  are inserted into complementary shaped recesses or core bearings  35  of the intake and exhaust channel cores. 
         [0042]    This final assembled arrangement of the bottom plate  1 , the cooling water core  12 , the cylinder head water core  25 , the intake channel core  32  and the exhaust channel core  33  is illustrated in  FIG. 4 . 
         [0043]      FIG. 5  shows the cooling water core  12 , the cylinder head water core  25 , as well as the intake channel core  32  and exhaust channel core  33  in a view from below. This view and also the representation of  FIG. 2  show that the straight annular segment  17  has a web  36 , here in the region of its end opposite the web  18 , which in the assembled cylinder head water core  25  spans the gap between the annular segment  17  and the cylinder head water core  25 . Moreover,  FIG. 5  shows a central passage  37  in the cylinder head water core  25 . The final cast cylinder head has in this region a roughly round opening, which is bored through, so that the cylinder head can accommodate a spark plug and/or an injection nozzle in this region. Thus, it is arranged adjacent to the annular segments  15  and  16 . 
         [0044]    In the cast cylinder head, the cooling channels for the valve seat rings of the cylinder head are produced according to the cooling water core  12  and the cavity to contain the cooling fluid of the actual cylinder head corresponds to the cylinder head water core  25 . Hence, to describe the cooling system of the cylinder head in the relevant cylinder segment one can rely directly on the representation of the figures, especially the representation of  FIG. 5 , where the flow through the cooling channels for the valve seat rings is illustrated with arrows by the cooling water core  12 . 
         [0045]    One notices from  FIG. 5  that the cooling fluid, starting from the cylinder head (bearing depression  9  of the bottom plate  1 ), goes to the injector bore (web  18  and straight annular segment  17 ). The cooling fluid at approximately half length of the injector bore (at the end of the web  18 ) enters the ring like cooling channels (annular segments  15  and  16 ) assigned to the two valve seat rings of the exhaust channels, while a portion of the cooling fluid continues to flow as far as the end of the injector bore (end of the straight annular segment  17 ) and there the cooling fluid divides among the two cooling channels (annular segments  15  and  16 ) and the channel (web  36 ) communicating with the flow of the actual cooling channel of the cylinder head. Consequently, the cooling fluid flows in the annular segments of the respective ring like cooling channel in the contrary direction, starting on the one hand from the beginning of the straight shared channel segment and on the other hand from the end of the shared straight channel segment (beginning of the straight annular segment  17  and end of the straight annular segment  17 ). In the region of the side of the respective annular segment opposite the injector bore, the cooling currents merge in an exit channel (web  20  and  22 ) and go from there to the drain channel to the crankcase (bearing depressions  10  and  11  in the bottom plate  1 ). In this embodiment, therefore, the cooling channels for the valve seat rings of the two exhaust valves have an inflow channel, by which the cooling fluid flows from the crankcase to the cylinder head, and moreover two outflow channels, from which the cooling fluid both from the cooling channels for the actual cooling of the cylinder head and also from the cooling channels for the valve seat rings drains away to the crankcase; finally, another flow connection is present from the injector bore to the cooling channel of the actual cooling of the cylinder head. 
         [0046]    In the region where the cooling fluid flows into the cooling channels for the valve seat rings (bearing element  19 ), the cooling flow divides and a portion of the cooling fluid gets directly into the actual cooling channels for the cylinder head (core projection  26 ). The cooling channels for the actual cooling of the cylinder head are finally connected via a cooling channel to the crankcase (interaction of core projection  29  and bearing depression  8 ); through this cooling channel, cooling fluid flows out from the cylinder head.