Patent Publication Number: US-2015083070-A1

Title: Arrangement comprising a cylinder head and a prechamber system

Description:
The present invention concerns an arrangement comprising a cylinder head and a prechamber system for an internal combustion engine having the features of claim  1 . 
     Particularly in the case of gas engines but also in the case of internal combustion engines in general prechamber systems can be used for ignition of a combustion mixture in a main combustion chamber. Those prechamber systems generally have a precombustion chamber in which a relatively easily ignitable combustion mixture can be ignited. An ignition flare is produced, which is fed to the main combustion chamber by way of a riser passage and bores. 
     That described prechamber system is generally arranged in a one-piece component which is then mounted in an opening in the flame plate. The term flame plate is used to denote that part of the cylinder head, that defines the main combustion chamber in the region of the ignition device—in this case therefore the prechamber system. 
     In most cases the prechamber component and the flame plate are those components of the internal combustion engine, that are exposed to the highest loadings. In particular some of the highest temperatures occur here during operation of the internal combustion engine. Consequently the service lives of the prechamber system and the flame plate are crucial factors for the longevity of internal combustion engines of the general kind set forth. 
     The object of the invention is to provide an arrangement comprising a cylinder head and a prechamber system, which allows increased service lives in comparison with the state of the art. 
     That object is attained by an arrangement having the features of claim  1 . 
     That is achieved in that there is provided a cooling cavity substantially surrounding the prechamber system and arranged in the flame plate and/or in that region of the prechamber system that is in the opening. The invention is based on the surprising realization that, in regard to service life, the thermal loading reduced by the cooling action offsets the mechanical weakening of the components involved. Those components, the flame plate and generally a prechamber component and seals if provided, therefore withstand the mechanical stresses occurring, in spite of the presence of the cooling cavity, and are capable of increased service lives by virtue of the reduced temperature. 
     Further advantageous embodiments of the invention are defined in the appendant claims. 
     The cooling cavity according to the invention can be implemented in a particularly simple fashion if the at least one prechamber component has a surrounding groove which together with an inside wall of the opening in the flame plate forms the cooling cavity, wherein the inside wall of the opening is arranged preferably substantially radially with respect to a longitudinal axis of the prechamber system. 
     A particularly preferred embodiment is one with passages for feeding and discharging a cooling medium, that are connected to the cooling cavity. The dissipation of heat can be improved by the continuous exchange of the cooling medium in the cooling cavity. 
     In order to avoid cooling medium issuing from the cooling cavity there are preferably provided two—preferably annular—seals for sealing off the cooling cavity. 
     A particularly simple structure for the passages can be achieved if the passages are—preferably completely—arranged in the flame plate. 
     In addition a particularly preferred embodiment is one in which the cooling cavity has an inlet opening and an outlet opening spaced from the inlet opening for temperature control medium, wherein the inlet opening and the outlet opening are respectively connected to passages. By virtue of the cooling medium which continuously flows past in operation the dissipation of heat which is made possible by the cooling cavity can be further improved and optimized. 
     Liquids can be used as the cooling medium. By virtue of their thermal capacity and their heat conduction properties water, aqueous mixtures or oil are particularly preferred in that respect. 
     It is however also possible to use gases, in particular compressed air, as the cooling medium. That has the advantage over liquids as the cooling medium that small leakage levels can be tolerated and therefore less complication and expenditure has to be involved for sealing off the cooling cavity and possibly the passages. 
     A further preferred embodiment is one in which the cooling cavity is substantially annular. That permits a uniform discharge of heat in all directions. 
     The cooling cavity can be adapted to the shape of the prechamber system by the cooling cavity being of a substantially polygonal cross-section with respect to a longitudinal axis of the prechamber system. The result is a further improvement in the dissipation of heat. 
     That applies in particular when the prechamber system includes a riser passage and bores for guiding an ignition flare to the main combustion chamber, the cooling cavity substantially surrounding the riser passage. 
     In addition protection is claimed for an internal combustion engine having a cylinder head according to the invention. 
    
    
     
       Further details and advantages of the invention will be apparent from the Figures and the related specific description. In the Figures: 
         FIG. 1  shows an arrangement according to the invention comprising a cylinder head and a prechamber system, and 
         FIG. 2  shows a diagrammatic sectional view through the arrangement according to the invention in the plane of the cooling cavity. 
     
    
    
       FIG. 1  shows a cylinder head  1  according to the invention with prechamber system  2  as a sectional view. In this embodiment the prechamber system  2  includes a precombustion chamber  15 , a riser passage  13  and a plurality of bores  14 . the prechamber system  2  is arranged in an opening  4  in the flame plate  3 . For the sake of simplicity of manufacture those parts of the prechamber system  2  are arranged in a single prechamber component  7 . The cooling cavity  6  surrounds the riser passage  13  in an annular configuration. 
     The cooling cavity  6  is formed substantially by a groove  8  in the prechamber component  7  together with an inside wall  9  of the opening  4 , in which the prechamber component  7  is arranged. Two seals  11  in the form of sealing rings are provided to seal off the cooling cavity  6 . 
     The shape of the cooling cavity  6  is matched to the tubular shape of the riser passage  13  insofar as a surface delimiting the cooling cavity  6 , facing towards the riser passage  13 , is in the shape of a cylindrical peripheral surface. Together with surfaces which serve to fix the seals  11  the arrangement involves a polygonal cross-section for the cooling cavity  6  radially with respect to a longitudinal axis L. 
     In this embodiment the prechamber system is substantially symmetrical with respect to the longitudinal axis L. That however is not essential for the invention. 
     The inside wall  9  of the opening  4  in the flame plate  3  has an inlet opening  17  and an outlet opening  18 . The cooling cavity  6  is connected to two passages  12  through those openings. Those passages  12  permit the feed and discharge of cooling medium to and from the cooling cavity  6 . In that respect the flow direction is indicated by arrows. 
     Simple manufacture of the passages is achieved by producing two bores which are at a right angle to each other, in the absence of the prechamber component  7 , wherein the one bore extends in the plane of the flame plate and the other perpendicularly thereto. That perpendicular bore makes it possible for cooling medium to be easily conveyed into the cooling jacket  16  of the cylinder head  1 . 
       FIG. 2  shows a diagrammatic section through the flame plate  3  and the prechamber system  2  in the plane of the cooling cavity  6 . The cooling cavity  6  surrounds the prechamber system  2  in the region of the riser passage  13 . Cooling medium is conveyed into the cooling cavity  6  through the inlet opening  17  by way of a passage  12  by a diagrammatically illustrated pump  19 . The flow indicated by arrows leaves the cooling cavity  6  through the outlet opening  18 . The cooling medium passes to the pump  19  again by way of the passage  12 . 
     Typically the pump  19  is so designed that flow speeds of between 0.5 m/s and 10 m/s are achieved in the cooling cavity  6 . 
     The present invention is not limited to the embodiment illustrated here. For example, instead of the groove  8  in the prechamber component  7  it is possible to provide a respective step in the prechamber component  7  and in the flame plate  3 , the steps cooperating to form the cooling cavity  6 . It is however also readily possible for the cooling cavity to be integrated into the prechamber component. A cooling cavity which is arranged in an annular configuration around the opening and which is spaced from the prechamber component  6  is however also conceivable.