Abstract:
A piston for an internal combustion engine wherein the piston includes a piston body fabricated from a metal and a piston head fabricated from a ceramic or ceramic composite material, the ceramic or ceramic composite piston head is press fit to the piston body and secured by an internal circumferential locking ring.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to internal combustion engines, and in particular to the pistons associated therewith wherein the piston body is fabricated from one material, preferably a metal, and the piston head is fabricated of ceramic or ceramic composite material and joined with the metal piston body. 
     2. Description of the Prior Art 
     Pistons are an integral part of most all internal combustion engines for the transfer of the power contained in the fuel/air mixture combustion to a crank shaft, which in turn through various gearing mechanisms transfers that power to the wheels of a land vehicle, the propeller of a water vehicle, or the propeller of an airplane. The piston is tightly fitted within the cylinder of an internal combustion engine and reciprocates upwardly and downwardly within the cylinder in response to the combustion of the fuel/air mixture, and the rotation of the crank shaft to which it is secured by means of a connecting rod. 
     The piston itself is normally fabricated of two primary elements. First there is the piston body, which is cylindrical in shape having a plurality of annular grooves for the receipt of piston rings to effectuate a seal with the wall of the cylinder within which it reciprocates. The piston body has means positioned on its underside for the secure connection of one end of a connecting rod, the opposing end being connected to a crank shaft. The upper portion of the piston body is normally fitted with a separately fabricated piston head which would normally be welded to the piston body about their common circumferential peripheries. It is the piston head which is exposed to the heat of combustion in the cylinder. It is also the piston head which has been the subject of much redesign in order to improve the combustion within the cylinder by inducing turbulence to create a more homogeneous combustion. Piston heads have evolved from a planar circular head, to heads having an upper surface resembling a single wedge shape or multiple wedge shapes to piston heads having a dome shape which are commonly referred to as hemi-heads. 
     Internal combustion engines which incorporate piston bodies and piston heads made of the same or similar metal material performed adequately with conventional fuels, such as gasoline and diesel. Engineers and designers would always look for improvements to the piston body and piston head arrangement in order to improve efficiency and performance. One drawback to the conventional piston body and piston head arrangement is that with both of the elements being fabricated from the same material, the heat of combustion within the cylinder will elevate the temperature of the piston head and the piston body due to their similar characteristics. This is not critical with respect to conventional internal combustion engines operating on conventional fuel, such as gasoline or diesel, since this heat transfer will not have deleterious affect until many hundreds of thousands of miles are put on the engine. 
     However, with the advent of use of alternative fuels such as ethanol, or natural gas, or hydrogen, there is a need because of the heat of combustion to seek alternative materials application to the fabrication of a piston head. An ideal material for the piston head would be that of a ceramic or ceramic composite, which performs superior to metal at high temperatures without deterioration or degradation. 
     Attempts have been made in the past to mate a ceramic piston head to a metal piston body, but those attempts have heretofore failed to provide for a metal piston body and ceramic piston head structure of sufficient durability normally resulting in separation of the body and head. 
     OBJECTS OF THE INVENTION 
     An object of the present invention is to provide for a novel piston structure for an internal combustion engine in which the piston body is fabricated of metal and the piston head is fabricated of ceramic or ceramic composite. 
     Another object of the present invention is to provide for a novel piston assembly in which the piston body and the ceramic/ceramic composite piston head are pressure locked. 
     A still further object of the present invention is to provide for a novel piston assembly in which a metal piston body and a ceramic/ceramic composite piston head are locked in secure relationship to each other under pressure by means of an internal lock frame. 
     A still further object of the present invention is to provide for a novel piston assembly, including a metal piston body and a ceramic/ceramic composite piston head which will allow for the use of alternative fuels within the internal combustion engine. 
     A still further object of the present invention is to provide for a novel piston assembly, including a metal piston body and a ceramic/ceramics composite piston head which will disrupt heat transfer from the heat of combustion of the fuel air mixture to the piston body and other engine parts. 
     SUMMARY OF THE INVENTION 
     A piston for an internal combustion engine wherein the piston includes a piston body fabricated from a metal and a piston head fabricated from a ceramic or ceramic composite material, the ceramic or ceramic composite piston head is press fit to the piston body and secured by an internal circumferential locking ring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects of the present invention will become apparent, particularly when taken in light of the following illustrations wherein: 
         FIG. 1  is a side view of a typical piston assembly; 
         FIG. 2  is a cross sectional exploded view of a typical piston and connecting rod assembly illustrating a planar piston head; 
         FIG. 3  is a cross-sectional view of the piston assembly of  FIG. 1  illustrating a wedge piston head; 
         FIG. 4  is a cross-sectional view of the piston assembly of  FIG. 1  illustrating a hemispherical piston head; 
         FIG. 5  is a side view of a ceramic piston head of the present invention; 
         FIG. 6  is an exploded partial cross-section view of a piston body and a piston head wherein the piston body is fabricated of metal and the piston head is fabricated of ceramic or ceramic composite, the figure further illustrating the manner in which the two elements are secured. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a side view of a typical piston assembly.  FIG. 2  is the cross-sectional exploded view of the piston assembly of  FIG. 1 . The piston assembly  10  comprises a piston body  12  cylindrical in cross-section having a plurality of annular grooves  14  for the receipt of one or more piston rings  16  which form the seal with the interior wall of a cylinder. The piston body  10  is partially hollowed defining a chamber  18  which is bisected by a connecting rod pin  20  in order to secure the upper end  22  of a connecting rod  24  to piston body  10 . The lower end  26  of the connecting rod  24  is secured to a crank shaft (not shown). A piston head  30  complimentary with the circumference of piston body  10  is positioned on the upper surface  28  of piston body  10 . The piston head  30  illustrated in  FIGS. 1 and 2  is planar and it is secured to the piston body by a circumferential weld  32 . 
     The piston illustrated in  FIGS. 1 and 2  represents the simplest assembly of a typical piston body  12  and piston head  30 , the piston head having a planar upper surface  34 . Attempts to improve the turbulence and compression within the cylinder has led to the development of a variety of different shaped piston heads secured to the piston body in the same manner described.  FIG. 3  is a cross-sectional view of a piston assembly in which the piston head  30  is forged or formed with a wedge shape  36 .  FIG. 4  is a cross-sectional view of a piston assembly in which the piston head  30  is forged or formed with a hemispherical shape  38 . In both instances, the piston head  30  and piston body  12  would be secured in the manner described. 
     The desire to incorporate a ceramic or ceramic composite piston head with a piston body has been hampered by the fact the ceramic or ceramic composite cannot be welded to the piston head. Therefore various means and attempts have occurred in which the ceramic or ceramic composite piston head is mechanically secured to the piston body. These attempts have failed because the mechanical securing means has proved unsatisfactory or has failed.  FIG. 5  is a side view of a ceramic piston head and  FIG. 6  is an exploded view of a metal piston body and a ceramic or ceramic composite piston head illustrating the manner in which the two elements are secured. 
     The piston body  40  is cylindrical in shape having an outer cylindrical surface  42  there being formed therein a plurality of annular grooves  44  for the receipt of a plurality of piston rings  16  which serve the same purpose as previously stated with respect to the prior art. The piston body  40  is also formed with an interior cylindrical surface  48  which is bisected at a point below its upper surface  50  by a connecting rod pin  20  for receiving and securing the upper end  22  of a connecting rod  24 . The interior cylindrical surface  48  of piston body  40  is further formed with an interior annular groove  52  which is formed proximate the upper portion of piston body  40 . Interior annular groove  52  will seat an annular portion of a locking ring  54 . 
     The ceramic or ceramic composite piston head  60  is formed of a ceramic or ceramic composite material which has a low coefficient of heat transmission. Ceramic or ceramic composite piston head  60  may be formed with a planar orientation, a wedge orientation, or hemispherical orientation. The ceramic or ceramic composite piston head  60  has an outer circumference  62  complimentary with the circumference of the piston body  40 . Extending downwardly from the lower surface  64  of the ceramic or ceramic composite piston head  60 , is a cylindrical member  66  whose circumference is substantially identical with the inner circumference of piston body  40 . Cylindrical member  66  may be in the form of a solid disk or it may be annular in configuration having its own outer and inner side walls. Cylindrical member  66  is designed to be inserted into the upper cylindrical opening  68  of piston body  40 . Cylindrical member  60  is formed with its own annular groove  70  onto which is fitted locking ring  54 . The design of ceramic or ceramic composite piston head  60  assures that when it is inserted into the upper opening of piston body  40 , that the annular groove  70  on cylindrical member  66  is in alignment with the interior annular groove  52  on the interior cylindrical surface  48  of piston body  40 . 
     Prior to insertion, locking ring  54  is fitted on the annular groove  70  of cylindrical member  66 . The locking ring  54  can be radially compressed such that when the ceramic or ceramic composite piston head  60  is punch fit into the piston body, locking ring  54  will compress slightly so as to accommodate the inner circumference of piston body  40 , and when the seating of the piston head  60  to piston body  40  is complete, with the annular groove  70  of cylindrical member  66  of piston head  60  in alignment with the interior annular groove  52  of piston body  40 , locking ring  54  will expand or rebound from its compressed state, and it will then be fully encapsulated by a portion of the annular groove  70  on cylindrical member  66  and the interior annular grove  52  of piston body  40 , thus locking and securing the ceramic or ceramic composite piston head  60  to the metal piston body  40 . 
     While the present invention has been described with respect to the exemplary embodiments thereof, it will be recognized by those of ordinary skill in the art that many modifications or changes can be achieved without departing from the spirit and scope of the invention. Therefore it is manifestly intended that the invention be limited only by the scope of the claims and the equivalence thereof.