Abstract:
In some aspects of the invention the invention will relate to conversion of an existing VW air cooled engine to liquid cooling, and in still further aspects it will relate to the design of a water jacket to maximize heat rejection of a combustion chamber and piston through perimeter cooling.

Description:
The present invention relates to internal combustion engines generally, and more particularly to internal combustion engines of the otto cycle type. In some aspects of the invention the invention will relate to conversion of an existing VW air cooled engine to liquid cooling, and in still further aspects it will relate to the design of water jacket to maximize heat rejection of a combustion chamber through perimeter cooling. 
   BACKGROUND OF THE INVENTION 
   The maximum power and efficiency that an internal combustion engine is capable of is limited by knock. This can occur when gasses during the compression stroke reach a temperature and pressure where they spontaneously combust. Cooling the combustion gasses allows higher pressures &amp; hence power and efficiency. 
   Another problem that exists in internal combustion engines, particularly those that are air-cooled, stems from the fact that rich mixtures are used to cool cylinder heads and or exhaust system to improve durability. This approach to cooling not only increases fuel consumption but it also increases the output of environmentally troublesome emissions. At maximum power with heads of this invention it is not necessary to operate with rich mixtures for cooling or to avoid knock. 
   In air and liquid cooled engines alike, the combination of cyclical thermal stresses and reduced material properties are causal factors leading to cracking. These cracks often occur between the inlet and outlet valves seats or spark plug holes. This area is generally the hottest temperature surrounding the combustion chamber, and in prior art heads often exceeds 475° F. At this temperature aluminums tensile and yield strength is half of what it is at 320° F. The heads of the present invention do not exceed 320 F. 
   In some prior art engines, including diesel engines, inadequate cooling of the heads produce warping that can interfere with the sealing necessary between the heads and cylinder block. 
   In the case of liquid cool automotive engines, the head and cylinder block are sealed by a gasket. This requires that the cylinder block be provided with a thick plate like top surface called a deck. The heads are likewise provided with a thick plate like structure adjacent to the combustion chamber. Between these two plate structures the gasket is squeezed to seal water and combustion gasses. These thick plate like structures are in the high temperature areas of the head, significantly reducing heat transfer from the combustion chamber and piston rings into the coolant. 
   Another problem that occurs in engines is when thermal expansion of the head produces excessive stress on the studs used to secure the head to the crankcase. Excessive stresses on these studs can cause distortion of cylinder bores and cracks in the crankcase. This is particularly true when the case is made of aluminum and/or magnesium. 
   Another problem is that the valves, ports and spark plugs reduce the area of contact between the coolant and combustion chamber. This is particularly true in cases where 4 or 5 valves per cylinder are used. As will be explained later, the intent of the present invention is to increase the surface area of contact between the coolant and combustion chamber by creating a skirt around the perimeter of the combustion chamber. In the preferred embodiment said skirt extends downward to encompass the piston and rings. 
   My objectives are to solve all of these problems. 
   It will become apparent to those skills in the art to which this invention relates how the problems listed above are solved by my invention. 
   These and still other objects and advantages of the invention will become apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiments taken with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view of the cylinder head normal to the cylinder axis of an opposed 4 cylinder engine. The section passes through the combustion chamber roof and extends through the coolant inlet and outlet ports. 
       FIG. 2  is a vertical sectional view taken approximately on the line  2 — 2  of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   There is shown in the drawings, one head of a horizontally opposed four-cylinder engine. The head is liquid cooled and as such  FIG. 1  is a sectional view that passes through the coolant inlet port and through the coolant outlet port. As best seen in  FIG. 2 ,  FIG. 1  passes through the dome shaped combustion chamber so that an irregularly shaped opening is seen. In between the coolant inlet port  10  and the coolant outlet port  12 ,  FIG. 1  passes through two cast aluminum cylindrical caps  14 , each of which is positioned over a respective cylinder barrel  16  shown by concentric lines. Each has four equally spaced ears  18  having openings  20  through each of which a hold down stud, not shown, passes. 
     FIG. 2  is a vertical transverse section that passes through the center of the exhaust valve seat  24  and valve guide  26  for the cylinder  16  shown at the right of  FIG. 1 .  FIG. 2  also shows the top end portion of the cylinder barrel  16  that has air-cooling fins  28  thereon.  FIG. 2  also shows the top end of a piston  30  having two compression rings  32  received in their respective grooves  34 . The piston is shown in its top dead center position. Above each piston is the dome shaped combustion chamber  22 . Between the top of the piston and the edge of the combustion chamber  22 , is what is called, the squish region  36  of the combustion chamber. 
   The head has a skirt  38  which extends down past the squish region  36  to below the bottom compression ring  32  of the piston when in its top dead center position. Inside the skirt  38  is a liquid cooling chamber  40  to which the coolant inlet port  10  and the coolant outlet port  12  communicate. The head also has an upper portion  42  of its cooling chamber that extends upwardly past the intake valves and exhausts valve seats  24  of each cylinder and then surrounds the exhaust valve guide  26 . Also shown in  FIG. 2  are two spark plug bosses  44 . As best shown by dotted lines in  FIG. 2 , the upper portion of the cooling chamber overlies the complete combustion chamber  22  except where it passes around the intake and exhaust passageways  46  adjacent the valve seats  24 . 
   The coolant inlet port  10  communicates with both the skirt cooling chamber  40  and the upper cooling chamber  42 , and there is a flow divider  48  that causes approximately equal flow through both chambers. Also as shown in  FIG. 1 , there is a flow divider  50  that causes liquid coolant to flow through the skirt passageway  52  between the cylinder caps  14 . 
   As previously stated, the piston is shown in its top dead center position in which the compression rings are cooled by the skirt having the liquid cooling chamber therein. This region will be referred to as region A. The area below the skirt all the way to the bottom dead center position of the piston will be referred to as region B. In  FIG. 2 , region B is cooled by airflow across and between the cylinder barrel cooling fins. Those skilled in the art would also recognize that the cylinder barrels could also be cooled by a separate water jacket instead of air fins. Depending on the length of the skirt  38 , it is also possible to eliminate external cooling of zone B entirely. The engine lubricating oil can remove the minimal heat required to be rejected in this region. The amount of heat which must be removed from the combustion chamber in region A is approximately 80%, while the heat which must be removed from region B is approximately 20% of the total heat that must be removed. Most of the heat that must be removed from the piston is actually removed through the compression rings when near their top dead center position. The heat that is removed in region B is removed through the air fins in depicted embodiment. Some heat however, is removed by the oil that is sprayed up onto the under side of the piston. 
   The top end of the cylinder under ambient conditions has a slip fit with respect to the inner walls of the skirt. This slip fit is designed so that under operating conditions the steel cylinder expands more than the aluminum head to provide solid contact and good heat transfer from the cylinder wall into the water jacket. The cylinders may also be pressed into the head to provide maximum heat transfer. 
   The stud columns  18  through which the hold down studs pass have approximately half of their outer surface exposed to the liquid coolant. In addition, water path  42  passes in between column  18  and the exhaust ports. This limits the thermal expansion of these mounting stud columns and thus the tension on the hold down studs by 40% over air-cooled heads. These thermally induced stresses in the mounting studs are notorious for causing cracks to develop in the crankcase in prior art designs. 
   As best seen in  FIG. 2 , the exhaust port above the valve seat turns directly out of the plane of the paper to the outlet connection for the exhaust system. The inlet port extends laterally in smooth arc path directly to the connection for the intake manifold. In prior art designs of air-cooled heads, the inlet port was shifted to allow air from the cooling fan to pass over the exhaust valve guide. This tortuous path of the intake port has limited the breathing capability and hence power output of the prior art design. In the present invention the exhaust valve guide is liquid cooled, thereby permitting a large non-torturous intake port and greater power output. 
   As previously stated aluminum material properties are significantly reduced at elevated temperatures. At the same time temperature is reducing the material properties it is inducing greater stresses. Typical liquid cooled heads reach 475 F in the bridge area between the intake &amp; exhaust valve seats. Air-cooled cylinder heads can go substantially ubove this temperature. Measurements of the head of the present invention have not exceeded 320 F in this region. In the prior art air-cooled heads that are cooled by a fan, the fan consumes as much as 25 horsepower. The mechanical fan can be eliminated when using the heads of the present invention. 
   It will be understood that while the heads shown and described were made to replace the air cooled heads of a VW engine, the principles described as well as others can be incorporated into other types of internal combustion engines be they of the diesel cycle or otto cycle type. 
   While this invention has been described in considerable detail I do not wish to be limited to these particular embodiments shown and described. It is my intention to cover hereby all adaptations, modifications and arrangements thereof, which will occur to those skilled in the art to which the invention relates. 
   SUMMARY 
   The present invention divides the cooling in an internal combustion engine into zone A and zone B. Zone A extends from the top dead center position of the pistons compression rings upwardly over the combustion chamber. Zone B is the area below zone A from which heat needs to be removed. Cylinder heads are provided with a dependent skirt having a liquid cooling passage therein which effects heat removal from the combustion chamber perimeter, piston, piston rings, the squish area, and the sealing surface between the cylinder and the cylinder head. Liquid coolant is introduced directly into the cooling chamber of the skirt and in addition a portion of it blankets the top of the combustion chamber to flow around the valve seats and valve guides. The intake port communicates the outside of the head to the intake valve in a smooth direct path, resulting in better breathing and greater horsepower. The coolant passageway through the skirt and the coolant passageway over the combustion chamber remove approximately 80% of the total heat to be removed. This water jacket is so efficient at removing heat from the combustion chamber that material properties are doubled over prior art heads at full load conditions. The better cooling of the heads results in greater efficiency, power, durability, longevity, less warpage, lower oil temperatures, and eliminates cracking of the case as occurs in prior art engines.