PISTON FOR INTERNAL COMBUSTION ENGINE
United States Patent 3613521
This specification discloses a cooling system for a piston formed of two parts and joined by brazing within annular grooves. Passages for cooling fluids are conveniently formed before the separate pieces are joined and are positioned such that the high temperature at common joined areas is effectively limited to prevent temperature deterioration of the bond between the two joined pieces. In addition, the cooling fluid transfers heat away from a head portion of the piston and means are provided to utilize as a cooling fluid a lubricating fluid normally present at a pin-bearing surface of the piston.
US Patent References:
Piston for internal-combustion engines
Mellor - June 1930 - 1763625
Wrist pin assembly
Kuttner - September 1946 - 2407429
Piston cooling construction
Graham - June 1948 - 2442408
Oil-cooled piston for a high speed internal combustion engine, particularly for a diesel motor for vehicles
Maybach et al. - August 1956 - 2759461
Multipart oil cooled internal combustion engine piston
Maier - November 1965 - 3215130
Piston for internal-combustion engines
Mellor - June 1930 - 1763625
Wrist pin assembly
Kuttner - September 1946 - 2407429
Piston cooling construction
Graham - June 1948 - 2442408
Oil-cooled piston for a high speed internal combustion engine, particularly for a diesel motor for vehicles
Maybach et al. - August 1956 - 2759461
Multipart oil cooled internal combustion engine piston
Maier - November 1965 - 3215130
Application Number:
04/862422
Publication Date:
10/19/1971
Filing Date:
09/30/1969
View Patent Images:
Export Citation:
Assignee:
Komatsu Manufacturing Co., Ltd. (Tokyo, JA)
Primary Class:
Other Classes:
123/41.350, 92/231, 29/888.044
International Classes:
F02F3/00; F02F3/22; F02F3/16; F16J1/00; F01B31/08; B23P15/10
Field of Search:
92/186,231,260,157,158,159 123/41.35,41.37,41.38,41.39 29/156.5,483
US Patent References:
Primary Examiner:
Schwadron, Martin P.
Assistant Examiner:
Cohen, Irwin C.
Claims:
What is claimed is
1. An internally cooled piston for internal combustion engines, said piston comprising:
2. A piston as in claim 1 wherein said upper half head portion is formed with a central void and means to provide fluid communication with said annular cooling canal.
3. A piston as in claim 2 which is normally lubricated with oil and including:
4. A piston as in claim 3 wherein said central void is hemispherically shaped and said means providing fluid communication are holes.
1. An internally cooled piston for internal combustion engines, said piston comprising:
2. A piston as in claim 1 wherein said upper half head portion is formed with a central void and means to provide fluid communication with said annular cooling canal.
3. A piston as in claim 2 which is normally lubricated with oil and including:
4. A piston as in claim 3 wherein said central void is hemispherically shaped and said means providing fluid communication are holes.
Description:
The present invention relates to a split-type internally cooled piston for internal combustion engines, and more particularly, the structure of the piston wherein the upper and lower portions are integrally joined by brazing.
As is generally known to those skilled in the art the recent internal-combustion engines have a tendency of high speed and the highly excessive feeding of fuel and therefore the heat calories expended within the cylinder is added and increased when compared with the heat discharging area, and therefore not only the cooling of the cylinder, but also the cooling of the reciprocating piston must be taken into consideration.
On the other hand, the usual piston is designed to minimize inertia in a high-speed engine and therefore to also satisfy the above-mentioned heat dissipation demands, an upper portion of the piston is usually made of a heat-resistant steel, and the lower portion thereof is made of aluminium alloy, and the joined portion of the two contains cooling canal, and the two portions are connected with bolt or screw, as is generally known.
However, the heat-resistant steel of the pistons of such a structure gravity and the heat conductivity thereof is smaller than that of aluminium alloy, and therefore the reduction of the weight of piston has natural limitation, and the discharge of heat cannot be effectively carried out, and there is a fear that the piston-supporting portion should be loosened through the usage.
Thus, in order to remove the drawbacks of the above mentioned pistons, there has been proposed such counter measures as to cast the whole piston with aluminium alloy, and in the casting process the cooling canal is cast out, but there are difficulties in the selection of the meltable core to be used in the formation of the canal, and in the maintenance of the dies, and the cost of production thereof is high, and there are such like problems.
The object of the present invention is to provide a piston having the brazen structure adopted for using alumium alloy, and the piston of this invention comprises two portions divided along a plane rectangular to the axis thereof and forming a joining surface, i.e., an upper half head portion and a lower half skirt portion. The upper half head portion is formed with an annular cooling canal exposed to the joining surface and extending around the axis of the piston, thereby to form a plurality of annular lands at the joining surface. On the other hand, the joining surface of the lower half skirt portion is formed with a plurality of shallow annular grooves adapted to accommodate the joining surface of the upper half head portion therein. The upper half and lower half portion can be integrally joined by filling a brazing material into the annular grooves and then fitting the annular lands into corresponding annular grooves.
BRIEF EXPLANATION OF THE DRAWING:
FIG. 1 is the cross-sectional view of the piston of the present invention;
FIG. 2 is the cross-sectional view at a point 90° away in the peripherical direction of FIG. 1; and
FIG. 3 is a diagram showing the temperature characteristic of the tensile strength of Y alloy and aluminum raw material.
The following are the explanations about an embodiment of the piston for internal-combustion engine of the present invention.
The piston shown in FIG. 1 and FIG. 2 is provided with the upper half head portion 2 made of aluminum alloy having the combustion chamber 1, and the lower half skirt portion 3 made of aluminum alloy having been separately prepared from the half of the head portion 2.
The upper half head portion 2 is mechanically processed in such a manner that in the casting process the annular cooling canal 5 formed on the joined surface 4, and the half spherical return chamber 6 inside the cooling canal, are cast, or the cooling canal 5 and return chamber 6 are mechanically processes in the preparatory processing after casting. In regard to the interval between said cooling canal 5 and the return chamber 6, they are connected by a plurality of radial form return paths 7, 7, 7, .... .
On the other hand, the lower half skirt portion 3 is produced in such a manner that the cavity 8 whose bottom is opened can be included, and on the side of the hole of the pin hole 9 into which the piston pin (not shown) is inserted, the oil groove 10 for supplying the cooling oil is provided by the cooperation of the piston pin, and said oil groove 10 is connected to the above mentioned cooling canal by means of the hole 12 which opens at the joined surface 11 On the other hand, in the center of the top surface of the half of the skirt portion 3, the outlet hole 13 for connecting said cavity 8 and said return chamber 6 of the upper half head portion 2, is provided, and the return oil is turned back to the lubricant oil chamber from said outlet hole 13.
On the other hand, on the joint surface 3a of the top surface of the half of the skirt portion 3, two lines of ring form grooves 14a and 14b for receiving said annular lands 2a and 2b are provided at the position corresponding to the annular lands 2a and 2b surrounding the inside and outside of the opening of said cooling canal 5.
Thus, on the inside and outside of the annular grooves 14a and 14b, the lands 15a, 15b and 15c for diving said ring form grooves 14a and 14b are formed.
Thus, in order to join the upper half head portion 2 and the lower half skirt portion 3 in the preparatory process, the two half portions are heated in an oven, and then a brazing material 16 is filled and melted in said annular grooves 14a and 14b.
In this case, when the lower half skirt portion 3 is kept horizontal, a brazing material 16 in the respective ring form grooves 14a and 14b is uniformly distributed all over the bottom of the grooves.
Thus, when the annular lands 2a and 2b of the half of the head portion 2 are agreed against the annular grooves 14a and 14b, the upper half head portion 2 and the lower half skirt portion 3 are correctly joined.
As is shown in FIG. 3, in regard to the tensile strength of Y alloy or aluminium alloy or such like joining materials to be used as raw material, it has the tendency to be lowered from about 200° C., but in the piston structure of the present invention, the mechanical strength of the joined portion is not lowered by the elevation of temperature.
Namely, the annular grooves 14a and 14b in which a brazing material 16 is filled, are placed in the down stream of the cooling canal 5, and therefore the heat received in the direction of the combustion chamber 1 of the upper half head portion 2 is effectively heated as the cooling canal 5, and the joined surface portion cannot be over heated.
On the other hand, the lubricant oil supplied into the cooling canal 5, stays at the bottom of the cooling canal 5, and it is moved by the movement of the piston, and therefore the heat conductivity is high, and the lubricant oil in the canal 5 is turned into the return chamber 6 from the paths 7, 7, 7,.... along with the movement of the piston, and it is let out through the outlet hole 13 from said return chamber 6.
In accordance with the present invention, the upper half head portion is formed with an annular cooling canal exposed to the joining surface and extending around the axis of the piston, thereby to form a plurality of annular lands at the joining surface, and the annular lands are used as brazing surfaces. Therefore, the surfaces to be joined by brazing can be cooled by the cooling oil circulating through the adjacent cooling canal. Thus, it is possible to maintain the surfaces joined by brazing at a low temperature as nearly same as that of the cooling oil (below 12° C.).
The joining by brazing is made by filling a brazing material into the shallow annular grooves of the lower half skirt portion and then fitting the annular lands into said grooves, so that there does not occur any wasteful flow-out of the brazing material and it is possible to distribute the molten brazing material and it is possible to distribute the molten brazing material evenly in the annular grooves and permit the flux to flow out in one direction so as to ensure complete and robust brazing. In this way, it becomes possible to obtain a strong and robust piston for internal-combustion engines which is joined by brazing.
As is generally known to those skilled in the art the recent internal-combustion engines have a tendency of high speed and the highly excessive feeding of fuel and therefore the heat calories expended within the cylinder is added and increased when compared with the heat discharging area, and therefore not only the cooling of the cylinder, but also the cooling of the reciprocating piston must be taken into consideration.
On the other hand, the usual piston is designed to minimize inertia in a high-speed engine and therefore to also satisfy the above-mentioned heat dissipation demands, an upper portion of the piston is usually made of a heat-resistant steel, and the lower portion thereof is made of aluminium alloy, and the joined portion of the two contains cooling canal, and the two portions are connected with bolt or screw, as is generally known.
However, the heat-resistant steel of the pistons of such a structure gravity and the heat conductivity thereof is smaller than that of aluminium alloy, and therefore the reduction of the weight of piston has natural limitation, and the discharge of heat cannot be effectively carried out, and there is a fear that the piston-supporting portion should be loosened through the usage.
Thus, in order to remove the drawbacks of the above mentioned pistons, there has been proposed such counter measures as to cast the whole piston with aluminium alloy, and in the casting process the cooling canal is cast out, but there are difficulties in the selection of the meltable core to be used in the formation of the canal, and in the maintenance of the dies, and the cost of production thereof is high, and there are such like problems.
The object of the present invention is to provide a piston having the brazen structure adopted for using alumium alloy, and the piston of this invention comprises two portions divided along a plane rectangular to the axis thereof and forming a joining surface, i.e., an upper half head portion and a lower half skirt portion. The upper half head portion is formed with an annular cooling canal exposed to the joining surface and extending around the axis of the piston, thereby to form a plurality of annular lands at the joining surface. On the other hand, the joining surface of the lower half skirt portion is formed with a plurality of shallow annular grooves adapted to accommodate the joining surface of the upper half head portion therein. The upper half and lower half portion can be integrally joined by filling a brazing material into the annular grooves and then fitting the annular lands into corresponding annular grooves.
BRIEF EXPLANATION OF THE DRAWING:
FIG. 1 is the cross-sectional view of the piston of the present invention;
FIG. 2 is the cross-sectional view at a point 90° away in the peripherical direction of FIG. 1; and
FIG. 3 is a diagram showing the temperature characteristic of the tensile strength of Y alloy and aluminum raw material.
The following are the explanations about an embodiment of the piston for internal-combustion engine of the present invention.
The piston shown in FIG. 1 and FIG. 2 is provided with the upper half head portion 2 made of aluminum alloy having the combustion chamber 1, and the lower half skirt portion 3 made of aluminum alloy having been separately prepared from the half of the head portion 2.
The upper half head portion 2 is mechanically processed in such a manner that in the casting process the annular cooling canal 5 formed on the joined surface 4, and the half spherical return chamber 6 inside the cooling canal, are cast, or the cooling canal 5 and return chamber 6 are mechanically processes in the preparatory processing after casting. In regard to the interval between said cooling canal 5 and the return chamber 6, they are connected by a plurality of radial form return paths 7, 7, 7, .... .
On the other hand, the lower half skirt portion 3 is produced in such a manner that the cavity 8 whose bottom is opened can be included, and on the side of the hole of the pin hole 9 into which the piston pin (not shown) is inserted, the oil groove 10 for supplying the cooling oil is provided by the cooperation of the piston pin, and said oil groove 10 is connected to the above mentioned cooling canal by means of the hole 12 which opens at the joined surface 11 On the other hand, in the center of the top surface of the half of the skirt portion 3, the outlet hole 13 for connecting said cavity 8 and said return chamber 6 of the upper half head portion 2, is provided, and the return oil is turned back to the lubricant oil chamber from said outlet hole 13.
On the other hand, on the joint surface 3a of the top surface of the half of the skirt portion 3, two lines of ring form grooves 14a and 14b for receiving said annular lands 2a and 2b are provided at the position corresponding to the annular lands 2a and 2b surrounding the inside and outside of the opening of said cooling canal 5.
Thus, on the inside and outside of the annular grooves 14a and 14b, the lands 15a, 15b and 15c for diving said ring form grooves 14a and 14b are formed.
Thus, in order to join the upper half head portion 2 and the lower half skirt portion 3 in the preparatory process, the two half portions are heated in an oven, and then a brazing material 16 is filled and melted in said annular grooves 14a and 14b.
In this case, when the lower half skirt portion 3 is kept horizontal, a brazing material 16 in the respective ring form grooves 14a and 14b is uniformly distributed all over the bottom of the grooves.
Thus, when the annular lands 2a and 2b of the half of the head portion 2 are agreed against the annular grooves 14a and 14b, the upper half head portion 2 and the lower half skirt portion 3 are correctly joined.
As is shown in FIG. 3, in regard to the tensile strength of Y alloy or aluminium alloy or such like joining materials to be used as raw material, it has the tendency to be lowered from about 200° C., but in the piston structure of the present invention, the mechanical strength of the joined portion is not lowered by the elevation of temperature.
Namely, the annular grooves 14a and 14b in which a brazing material 16 is filled, are placed in the down stream of the cooling canal 5, and therefore the heat received in the direction of the combustion chamber 1 of the upper half head portion 2 is effectively heated as the cooling canal 5, and the joined surface portion cannot be over heated.
On the other hand, the lubricant oil supplied into the cooling canal 5, stays at the bottom of the cooling canal 5, and it is moved by the movement of the piston, and therefore the heat conductivity is high, and the lubricant oil in the canal 5 is turned into the return chamber 6 from the paths 7, 7, 7,.... along with the movement of the piston, and it is let out through the outlet hole 13 from said return chamber 6.
In accordance with the present invention, the upper half head portion is formed with an annular cooling canal exposed to the joining surface and extending around the axis of the piston, thereby to form a plurality of annular lands at the joining surface, and the annular lands are used as brazing surfaces. Therefore, the surfaces to be joined by brazing can be cooled by the cooling oil circulating through the adjacent cooling canal. Thus, it is possible to maintain the surfaces joined by brazing at a low temperature as nearly same as that of the cooling oil (below 12° C.).
The joining by brazing is made by filling a brazing material into the shallow annular grooves of the lower half skirt portion and then fitting the annular lands into said grooves, so that there does not occur any wasteful flow-out of the brazing material and it is possible to distribute the molten brazing material and it is possible to distribute the molten brazing material evenly in the annular grooves and permit the flux to flow out in one direction so as to ensure complete and robust brazing. In this way, it becomes possible to obtain a strong and robust piston for internal-combustion engines which is joined by brazing.