Abstract:
A method for machining a cylinder head including a cooling jacket, wherein the fire deck of the cylinder head which is in a raw state is machined by material removal in relation to a reference mark of the cylinder head. The position of the cooling jacket is used as a reference mark.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method for machining a cylinder head comprising a cooling jacket, with the fire deck of the cylinder head which is in a raw state being machined by material removal in relation to a reference mark of the cylinder head. The invention further relates to a cylinder block for a liquid-cooled internal combustion engine with a cylinder or a group of cylinders which consist of several cylinders Which are cast together, comprising a liquid compartment which encloses the cylinder or group of cylinders and which is enclosed by an outside wall, with gaps being provided between the cylinder or the outer cylinders of the group of cylinders and the outside wall of the cylinder block through which the cooling liquid flows from one side to the other side of the cylinder or the group of cylinders, with at least one plug which reduces the cross section being arranged in at least one gap. 
     2. The Prior Art 
     In order to fulfill predefined tolerance requirements for the wall thickness between fire deck and cooling jacket, machining by material removal of the fire deck of a cylinder head is necessary. It is known to use sprue cut-offs in the gas exchange ports in the region of the valve guide cut-offs as reference marks for machining by material removal. This leads to the disadvantage however that relatively large tolerances need to be taken into account for the wall thickness of the fire deck in the region of the valve reinforcing ribs on the exhaust side. In the most extreme of cases, this may lead to insufficient cooling of the valve reinforcing ribs on the exhaust side. 
     A cylinder block is known from DE 198 40 379 A1 in whose cooling liquid chamber a plug which reduces the flow cross section is arranged in the region of a gap between an outer cylinder and the outside wall of the cylinder block. A defined minimum quantity of cooling fluid is able to pass the plug via cooling-fluid passages. 
     It is the object of the invention to avoid this disadvantage and to ensure sufficient cooling, especially the valve reinforcing ribs on the exhaust side. It is a further object of the invention to enable a purposeful control of the coolant flow in the cylinder block. 
     SUMMARY OF THE INVENTION 
     This is achieved in accordance with the invention in such a way that the position of the cooling jacket is used as a reference mark. It is preferably provided that a defined wall region of the cooling jacket is used as a reference mark. 
     Very narrow tolerance ranges for the wall thickness of the fire deck in the region of the valve reinforcing ribs can be fulfilled because reference marks of the cooling jacket are used as reference quantities for machining by material removal. 
     It is especially advantageous in this respect when the wall thickness between a wall region of the cooling jacket and the fire deck is used as a reference mark in the region of least one valve reinforcing rib, especially an exhaust valve reinforcing rib. 
     A purposeful control of the coolant flow in the cylinder block can be achieved when the plug is arranged in a water transfer port to or from the cylinder head. Retroactive insertion is possible due to the fact that the plug is arranged in a transfer port. The plug preferably has a sickle-shaped cross section, with the plug preferably being pressed against the wall of the transfer port by a positioning bracket which is preferably rigidly connected with the plug. In order to prevent wrong mounting, it is especially advantageous when the transfer port has a substantially oblong cross section, with preferably the plug being insertable in an interlocking fashion and only in a defined position in the transfer port. 
     It is especially advantageous for the control of the cooling liquid flow when the plug is arranged in the region of a lateral inlet port for the liquid into the liquid chamber, with the convex side of the plug facing the incoming cooling liquid. 
     The plug can consist of plastic, aluminium, or of steel, e.g. deep-drawing sheet steel. Since 100% sealing by the plug is not required, temperature tensions can be avoided by sufficient play between plug and the cylinder block. 
     The invention will now be explained in greater detail by reference to the drawings. 
    
    
     
       BRIEF DESCRITON OF THE DRAWINGS 
         FIG. 1  shows a cylinder head of an internal combustion engine in a cross-sectional view; 
         FIG. 2  shows a cylinder block in accordance with the invention in a top view; 
         FIG. 3  shows the detail III of  FIG. 2  of the cylinder block; 
         FIG. 4  shows the cylinder block in a sectional view along line IV-IV in  FIG. 8 ; 
         FIG. 5  shows the detail V of  FIG. 4  of the cylinder block; 
         FIG. 6  shows a cylinder-head sealing surface of the cylinder block in a detailed oblique view; 
         FIG. 7  shows the cylinder-head sealing surface in a further oblique view; 
         FIG. 8  shows a cylinder block in accordance with the invention in a longitudinal view along line VIII-VIII in  FIG. 5 , and 
         FIG. 9  shows a plug in an oblique view. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The cylinder head  1  as shown in  FIG. 1  comprises a cooling jacket  3  adjacent to the fire deck  2  for receiving cooling liquid and gas exchange ports  4  and  5 . Reference numeral  6  indicates the central receiving area for an injection device (not shown in greater detail). 
     In order to fulfill predefined tolerance requirements for the wall thickness s of fire deck  2 , the cast raw cylinder head is subjected to machining by material removal of the fire deck  2 , with the machining occurring in relation to a reference mark of cylinder head  1 . 
     According to the present invention, the cooling jacket  3  or a defined wall region  3   a ,  3   b ,  3   c  or the wall thickness s of the fire deck  2  in the region of at least one valve reinforcing rib  8  itself, e.g., an exhaust valve reinforcing rib, is used as a reference mark  7 . The wall thickness s can be determined and monitored with a known destruction-free measuring method, e.g., an ultrasonic or X-ray method. This allows fulfilling much narrower tolerance requirements than before and ensuring sufficient cooling and strength of the cylinder head  1 . 
     A cylinder block  101  comprises a group  102  of several cylinders  103  which are arranged in series ( FIGS. 2  to  FIG. 9 ). Cylinders  103  are enclosed by cooling liquid in a liquid compartment  104 , with the cooling liquid flowing into the liquid compartment  104  via a lateral inlet  105 . Reference numeral  101   c  designates the cylinder head sealing surface of the cylinder block  101 . Gaps  107 ,  108  are formed between the outer cylinders  103  and the outside wall  106  of the cylinder block  101  through which the cooling liquid can flow from one side  101   a  of the cylinder block  101  to the other side  101   b . Between the individual cylinders  103 , no flow connection is provided in the embodiment between the sides  101   a ,  101   b  of the liquid compartment  104 . A plug  110  of a substantially sickle-shaped cross section is arranged directly in the region of the inlet  105  in a transfer port  109  between the cylinder block  101  and the cylinder head (not shown in greater detail). The transfer duct  109  has a substantially pear-shaped cross section. In order to ensure the positioning of the plug  110  in the transfer duct  109  which is positionally correct, the plug  110  comprises positioning brackets  111  which press the plug  110  with its convex outside  110   a  against the concave wall  109   a  of the transfer duct  109 . The convex outside  110   a  of plug  110  faces the cooling liquid flowing in via the inlet port  105 . The plug  110  can be inserted in an interlocking fashion and correctly positioned into the transfer port  109  as a result of the precisely defined cross sections of plug  110 , so that wrong installation can be excluded. 
     The cooling fluid flows through the inlet port  105  according to the arrows S into the liquid compartment  104  and reaches through gap  107  to the other side  101   b  of cylinder block  101 , with the cooling liquid being guided by the plug  110  in the direction of gap  107 . Thereupon liquid flows around the cylinders  103  at one side  101   b  in the longitudinal direction of the cylinder block  101 . 
     The cooling liquid finally reaches the side  101   a  of the cylinder block  101  via gap  108  and flows around the cylinder  103  in the longitudinal direction in the direction towards the transfer port  109 . The cooling liquid is now guided through the transfer port  109  in the direction of the cylinder head by the plug  110 . 
     As is shown in  FIG. 8 , a total sealing of the liquid compartment  104  by the plug  110  is neither provided nor desired, so that a short-circuit flow L of small quantities of liquid is possible via defined leakages  112 . 
     The plug  110  itself can consist of plastic or aluminium. A defined play to the cylinder block  101  should be provided especially in the case of arrangements with aluminium in order to avoid temperature tensions.