Abstract:
A cylinder head for a combustion cylinder of an internal combustion engine is provided, which has at least one inlet opening and at least one outlet opening, as well as gas exchange valves which are operable by electrohydraulic valve actuators, some of which gas exchange valves function as inlet valves to control the at least one inlet opening, and some of which gas exchange valves function as outlet valves to control the at least one outlet opening. For the purpose of producing a compact, complete module which, as a separate component, may be tested for reliability and may be installed into the engine block of the internal combustion engine without additional preassembly effort, the cylinder head is provided with at least one high pressure line for supplying fluid under high pressure and at least one recycling line for recycling fluid, which have coupling openings for the hydraulic coupling of the valve actuators, and also means for fastening the valve actuators are provided.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a cylinder head for a combustion cylinder of an internal combustion engine. 
   BACKGROUND INFORMATION 
   In an internal combustion engine having electrohydraulic valve control, a type of which is described, for example, in published German patent document DE 198 26 047, fluid under high pressure, e.g., hydraulic oil, is supplied to the electrohydraulic valve actuators for operating the gas exchange valves, and, at the same time, fluid under low pressure is carried off from the valve actuators and fed back to a fluid reservoir. The valve actuators each have a double-acting working cylinder having an operating piston, which is shiftable inside the cylinder, connected to the associated gas exchange valve, which subdivides the working cylinder into two hydraulic working chambers. By appropriate pressure control of the fluid in the working chambers using two electrical control valves, e.g., 2/2-way solenoid valve, the operating piston is shifted into one or the other direction, and thereby the associated gas exchange valve is opened in a defined manner or closed completely. 
   SUMMARY 
   The cylinder head according to the present invention has the advantage that, together with the mounting of the valve actuators for operating the gas exchange valves, the fluid supply of the valve actuators is produced at the same time. The cylinder head equipped with the valve actuators forms a compact module, which may be tested for reliability as a separate component and delivered to the customer. The customer only has to set the module onto the combustion cylinders of the motor block, and, without additional preassembly effort, the customer is thus able to obtain the internal combustion engine having a structurally prearranged, functionally tested electrohydraulic valve control. 
   According to one example embodiment of the present invention, two line pairs are present which are each formed by one high pressure line and one return line, which may run parallel to each other at the cylinder head. One pair of lines has the coupling openings for the valve actuators of the inlet valves, and the other pair of lines has the coupling openings for valve actuators of the outlet valves. 
   By these measures, the fluid supply takes place for the inlet and the outlet side via separate hydraulic lines, which are also referred to as rails. 
   According to one example embodiment of the present invention, the high pressure lines and the recycling lines are integrated into the cylinder head, i.e., they are produced either when the cylinder head is cast, or by a further processing procedure, for example, by drilling or cutting. 
   According to one example embodiment of the present invention, the high pressure lines are designed as separate components and fixed to the cylinder head. This makes possible the use of materials which have a greater strength than the cylinder head which is usually manufactured by die casting aluminum. In this context, high pressure lines may be clamped to the cylinder head using retaining clips, which, on their part, are screwed to the cylinder head. Alternatively, it is also possible to cast in the high pressure lines by laying them into the mold as the core during die casting, and thus having the material of the cylinder head flow around them. 
   According to one example embodiment of the present invention, the means for fixing the valve actuators at the cylinder head have centering openings and threaded holes which are put into the outer cylinder head surface, the centering openings being used at the same time for putting through the valve shafts of the gas exchange valves. 
   According to one further example embodiment of the present invention, at least one leakage line is also provided in the cylinder head for recycling leakage fluid which are connected to the centering openings via connecting channels. In this context, one leakage line is may be allocated to each line pair of a high pressure line and a recycling line, which runs parallel to the line pair and is integrated into the cylinder head. Fluid leakages in the valve actuators are carried off via the leakage lines, and in this context, may be separated for the inlet and outlet side. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a top view of a cylinder head for a combustion cylinder of an internal combustion engine according to the present invention. 
       FIG. 2  shows a cutout view of a section along line II—II shown in FIG.  1 . 
       FIG. 3  shows a perspective view of a cylinder head shown in  FIG. 1 , preassembled into a complete module that is able to be functionally tested by having valve actuators set on it. 
       FIG. 4  shows a perspective view of an actuator housing of the valve actuator shown in FIG.  3 . 
       FIG. 5  shows a side view of the actuator housing in the direction of arrow V in FIG.  4 . 
       FIG. 6  shows a cutout view of a section along line VI—VI shown in FIG.  5 . 
       FIG. 7  is a block diagram of a valve actuator for illustrating the functions. 
   

   DETAILED DESCRIPTION 
   Cylinder head  10  for a combustion cylinder for an internal combustion engine, as shown in a top view in FIG.  1  and in a sectional view in  FIG. 2 , is provided with four gas exchange valves  11 , of which only valve shafts  111  are shown in  FIGS. 1 and 2 . 
   In  FIG. 7 , a cutout of cylinder head  10  in the region of a gas exchange valve  11  is shown in section. The gas exchange valve  11  closes off an opening  12  in cylinder head  10 , which, on its part, is set up on the combustion cylinder, and closes off a combustion chamber developed in the combustion cylinder in a gastight manner. Gas exchange valve  11  has a valve seat  13 , which encloses opening  12  in cylinder head  10 , and a valve element  14  having a valve closing body  142 , sitting on an axially, shiftably guided valve shaft  141 , which cooperates with valve seat  13  for closing and freeing opening  12 . By displacement of valve shaft  141  in one axial direction or the other, valve closure element  142  lifts off from valve seat  13  or seats itself on valve seat  13 . 
   As seen in  FIGS. 1 and 2 , of the four gas exchange valves  11 , in each case two are situated side by side, and the two pairs of gas exchange vales  11  are placed centrosymmetrically on cylinder head  10 . In this context, one pair of gas exchange valves  11  forms inlet valves  111 , and another pair of gas exchange valves  11  placed centrosymmetrically to it forms outlet valves  112  for the combustion chamber in the combustion cylinder. Each inlet valve  111  controls an inlet opening  12  using its valve member  142 , and each outlet valve  112  controls an outlet opening  12  using its valve member  142 . 
   Each gas exchange valve  11  is operated by an electrohydraulic valve actuator  15 . The construction and the operation of electrohydraulic valve actuator  15  are conventional (cf published German patent document DE 198 26 047), and an example embodiment is shown in  FIG. 7  as a block diagram. Valve actuator  15  has an actuator housing  16 , in which a double-acting, hydraulic working cylinder  17  and two electrical control valves  18 ,  19 , designed, for example, as a 2/2-way solenoid valves, are accommodated. An operating piston  20 , connected to valve shaft  141  of exchange gas valve  11 , is movably guided in working cylinder  17 , and it subdivides working cylinder  17  into a lower working space  21  and an upper working space  22 . Lower working space  21  is connected directly, and upper working space  22  is connected via first control valve  18 , to a fluid inflow opening  23  in actuator housing  16 . Upper working space  22  is also connected to a fluid outlet opening  24  in actuator housing  16  via second control valve  19 . The piston surface of operating piston  20  bordering on upper working space  22  is greater than the piston surface of actuator piston  20 . Control valves  18 ,  19  are controlled electrically, for which electrical connecting contacts  25 ,  26  are present at actuator housing  16 . 
   In FIG.  4  and  FIG. 5 , activator housing  16  is shown (without a hydraulic working cylinder and electrical control valves) in two different views. Fluid supply opening  23  and fluid outflow opening  24  are situated in a planar housing surface  161 . Concentric with fluid supply opening  23 , a ring groove  31  is provided in the housing surface  161 , and concentric with fluid outflow opening  24 , a ring groove  32  is provided in the housing surface  161 , which are used for accommodating a sealing ring not shown here. In the same housing surface  161 , a leadthrough passage  28  ( FIG. 6 ) concentrically enclosed by a hollow stud  27  projecting from housing surface  161  has been put in. Coaxial to leadthrough passage  28  and hollow peg  27 , a hollow space  47  is situated in actuator housing  16 , for accommodating working cylinder  17 . In addition, two blind hole accommodating chambers  29 ,  30  are provided, which open out on housing surface  162  that faces away from housing surface  161  (FIG.  5 ). Accommodating chambers  29 ,  30  are used to accommodate control valves  18 ,  19 , which are pushed into accommodating chambers  29 ,  30  from the direction of housing surface  162 . As shown by the sectional representation in  FIG. 6  for accommodating chamber  30 , which may be seen as a cutout, a connecting channel  33  runs from the bottom of accommodating chamber  30  to the inside of hollow peg  27 , via which a fluid leakage, exiting at electrical control valve  18 , may be carried off to leadthrough passage  28 . Although not shown in  FIG. 6 , the same kind of connecting channel leads to accommodating chamber  29 . As shown in  FIGS. 4 and 5 , protruding lugs are formed onto the narrow sides, facing away from each other, of actuator housing  16 , in each of which protruding lugs a leadthrough bore  35  is provided for leading through fastening means, e.g., a screw  36  (FIG.  3 ). Leadthrough bores  35  run parallel to the axis of hollow stud  27 . 
   In  FIG. 3 , actuator housing  16  is completed by working cylinder  17  and control valves  18 ,  19  in an example embodiment. In each case, one valve actuator  15  is used to operate a gas exchange valve  11 , so that in the case of cylinder head  10  shown in  FIG. 1 , four valve actuators have to be fastened to cylinder head  10  using four exchange valves  11 , in each case valve shaft  141  of allocated gas exchange valve  11  having to be coupled to operating piston  20  in working cylinder  17 . 
   Now, cylinder head  10  may be viewed in such a way that when valve actuators  15  are set upon cylinder head  10  and fastened to cylinder head  10 , the fluid supply of valve actuators  15  is ensured. As shown in  FIGS. 1 and 2 , for this purpose, two high pressure lines  37 , so-called high pressure rails, are provided, for supplying fluid under high pressure to valve actuators  15 , and two recycling lines  38 , so-called recycling rails, are provided for carrying off fluid under low pressure from valve actuators  15  for the purpose of recycling to a fluid reservoir. High pressure lines  37  and recycling lines  38  run parallel to each other, and a pair of lines consisting of a high pressure line  37  and a recycling line  38  is allocated to inlet valves  111 , and another pair of lines consisting of high pressure line  37  and a recycling line  38  is allocated to outlet valves  112 . High pressure lines  37  and recycling lines  38  are furnished with coupling openings  39  and  40 , respectively, for the hydraulic coupling of valve actuators  15 . The number of the coupling openings  39  in high pressure lines  37  is equal to the number of coupling openings  40  in recycling lines  38 , and corresponds to the number of inlet valves  111  and outlet valves  112 , respectively. In the exemplary embodiment of  FIGS. 1 and 2 , high pressure lines  37  are designed as separate components, which are firmly clamped on cylinder head  10  using retaining clips  41 , which, on their part, are screwed to cylinder head  10 . Recycling lines  38  are integrated into cylinder head  10  and are produced either already at the time cylinder head  10  is cast, or are drilled into cylinder head  10  by an additional processing procedure. Furthermore, in cylinder head  10 , leakage lines  42 , also referred to as leakage rails, are also integrated, which are produced in the same way as recycling lines  38 . One leakage line  42  is allocated to each pair made up of high pressure line  37  and recycling line  38 , and the leakage line  42  runs parallel to high pressure line  37  and recycling line  38 . 
   For the purpose of coupling valve actuator  15  to cylinder head  10 , fixing means are provided on cylinder head  10 , which include centering openings  43  and threaded holes  44 . Each centering opening  43  accommodates hollow peg  27 , which protrudes from the actuator housing of valve actuator  15 , in a form-locking manner, while threaded holes  44  are placed congruently with the two leadthrough bores  35  present at each actuator housing  16 . Centering openings  43  are used at the same time for guiding through valve shafts  141  of gas exchange valves  11 . Furthermore, coupling openings  39 ,  40  are situated in such a way that, when actuator housings  16  are mounted using hollow studs  27  submerging into centering opening  43 , fluid supply openings  23  set themselves congruently on coupling openings  39  in high pressure line  37 , and fluid outflow openings  24  set themselves congruently on coupling openings  40  in recycling line  38 . The sealing rings lying in ring grooves  31 ,  32  provide for a liquid-tight connection between fluid supply and fluid removal openings  23 ,  24  in actuator housing  16  and coupling openings  39 ,  40 , when actuator housings  16  are pressed onto cylinder head  10  by screwing down screws  36  in threaded holes  44 , which are guided through leadthrough bores  35  on actuator housing  16 . By setting hollow pegs  27  into centering openings  43 , valve shafts  141  of gas exchange valves  11 , extending through centering openings  43 , are simultaneously coupled to operating pistons  20  of working cylinders  17 . 
   As seen from the sectional representation in  FIG. 2 , centering openings  43  are connected to leakage lines  42  via connecting channels  45 , and specifically, centering openings  43  allocated to inlet valves  111  are connected to leakage line  42 , and centering openings  43 , which are allocated to outlet valves  112 , are connected to the other leakage line  42 . By the use of these connecting channels  45 , the fluid leakages occurring in valve actuators  15 , i.e., on the one hand, at working cylinder  17  and, on the other hand, in control valves  18 ,  19 , are conducted into leakage lines  42  and from there recycled into a fluid reservoir. 
     FIG. 3  shows cylinder head  10  equipped with four valve actuators  15 , which represent a compact, complete module having a functionally testable electrohydraulic valve control, which additionally only has to be mounted gas-tight on a combustion cylinder in the motor block of an internal combustion engine and connected to a fluid supply system. In this context, in the drawings only a one-cylinder variant is shown. By concatenating several such modules according to  FIG. 3 , it is possible to implement in-line engines and V engines having any number of cylinders. For this, high pressure lines  37 , recycling lines  38  and leakage lines  42  are designed at their ends in such a way that, for coordination of a like module, the ends of the lines  37 ,  38 ,  42  that are put together may be fitted into one another in a liquid-tight manner or may be otherwise joined together in a liquid-tight manner. As  FIG. 3  makes clear, in this connection high pressure lines  37  are plugged into one another using appropriately designed projections  371  and  372 , while high pressure lines  37  and leakage lines  42  open out into flanges  46 , which are set together flat while a seal is placed between them, and screwed together with each other. Alternatively, it is also possible to produce multi-cylinder variants in one part, i.e., to cast all cylinder heads in one piece. All the lines or rails  37 ,  38 ,  42  are then drilled through the entire multicylinder head, and all the cylinders are supplied through the rails. 
   The present invention is not limited to the above-described exemplary embodiments. Thus, for example, recycling lines  38  may be cast as a separate component onto cylinder head  10 . In order to do that, high pressure lines  37  are laid like a core into the mold during the mold casting process, so that they have the material of cylinder head  10  flowing around them, and thereby a connection to cylinder head  10  is created. 
   High pressure lines  37  may be integrated into cylinder head  10  just as are recycling lines  38  and leakage lines  42 , in that they are produced during the casting of cylinder head  10 , or are drilled during a further operating procedure. The advantage of high pressure lines  37  produced as separate components is the possibility of using materials having a greater strength than the aluminum die casting of cylinder head  10 .