The present invention relates to a piston for an internal combustion engine. More particularly, the present invention relates to an arrangement and process for manufacture of steel piston with cooling gallery for highly rated internal combustion engines.
BACKGROUND OF THE INVENTION
[0001] Internal combustion engines generally use pistons made out of Aluminium alloys. However, there is constant demand for increasing the performance and improving emission levels, leading to higher firing pressures and temperatures in cylinder components. Steel is the chosen alternative to Aluminium in such highly rated applications. Generally, the piston suffers periodic mechanical and thermal loadings due to prolonged exposure to the combustion chamber. Excessive piston temperature can cause oxidation or severe degradation, which eventually leads to poor engine performance. Hence these pistons often are provided with a cooling gallery at underside of crown and at the back of the ring belt. Lubricating oil is pumped into the cooling gallery through a nozzle jet. The intimate contact of engine oil on the gallery surfaces enhance the heat transfer process due to cocktail action from the piston reciprocation.
[0002] It is advantageous to provide a reliable and cost-efficient piston with a cooling gallery having oil retaining plates for internal combustion engine, as described in greater detail herein.
SUMMARY OF THE INVENTION
[0003] The following summary is provided to facilitate an understanding of some of the innovative features unique to the disclosed embodiments and is not

intended to be a full description. A full appreciation of the various aspects of the embodiments disclosed herein can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
[0004] It is, therefore, one aspect of the present invention to provide for an improved piston with a cooling gallery having oil retaining plates for internal combustion engine, which is filled with adequate oil for cooling of the piston.
[0005] It is another aspect of the present invention to provide for a piston with cooling gallery having the oil retaining plates, which can retain oil for sufficient time to provide cooling of the piston.
[0006] It is yet another aspect of the present invention to provide an improved piston with cooling gallery having the oil retaining plates, which is reliable, light weight and cost-efficient, for heavy duty high specific output and ultra-low emission internal combustion engines.
[0007] In one aspect of the present invention, a piston for an internal combustion engine is disclosed which includes a crown portion having an upper combustion chamber and a ring belt region with a plurality of ring grooves. A pair of pin bosses from the crown portion includes a pin bore that supports a wrist pin. A cooling gallery is located between the ring belt region and the combustion chamber on a bottom surface of a piston head. A pair of semi-circular retaining plates with an inlet gap and an outlet gap is positioned at a bottom side of the cooling gallery and at back side of the ring belt region to close the cooling gallery. The retaining plates provide a passage for oil jet to enter the cooling gallery via the inlet gap, retain and circulate the oil to reduce surface temperature of the piston and exit through via the outlet gap.
[0008] The inner peripheral surface of the retaining plates are anchored to the cooling gallery in a groove and supported in a step machined at the back side of the ring belt region. The outer surface of the retaining plates is welded to the cooling gallery in a step machined at the back side of the ring belt region. The inlet gap and

the outlet gap of the retaining plates are positioned diametrically opposite to each other with respect to the piston. The inlet gap provides passage of oil to the gallery by means of a continuous flow or stream of oil from a crank sump supply source. The oil is retained in the cooling gallery for sufficient time to provide cooling of the piston. The gap between retaining plates are positioned in such a way as to provide passage for oil jet to enter the cooling gallery and exit through diametrically opposite gap between the plates. The piston is made of single forged piece of steel material and the two annular semi-circular retaining plates are made from a steel material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The disclosed embodiments may be better understood by referring to the figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention.
[0010] FIG. 1 illustrates a cross-sectional view along the thrust axis of a piston, in accordance with an exemplary embodiment of the present invention;
[0011] FIG. 2 illustrates a cross-sectional view of the piston along the pin axis having a cooling gallery with a pair of annular semi-circular retaining plates, in accordance with an exemplary embodiment of the present invention;
[0012] FIG. 3 illustrate a perspective view of the annular semicircular retaining plates, in accordance with an exemplary embodiment of the present invention;
[0013] FIG. 4 illustrates a detailed view of the cooling gallery with the retaining plates, in accordance with an exemplary embodiment of the present invention; and

[0014] FIG. 5 illustrates a sectional view of the piston looking from theopen end towards underside of a crown portion, in accordance with an exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof.
[0016] In the following, numerous specific details are set forth to provide a thorough description of various embodiments. Certain embodiments may be practiced without these specific details or with some variations in detail. In some instances, certain features are described in less detail so as not to obscure other aspects. The level of detail associated with each of the elements or features should not be construed to qualify the novelty or importance of one feature over the others.
[0017] The claimed subject matter has been provided here with reference to one or more features or embodiments. Those skilled in the art will recognize and appreciate that, despite the detailed nature of the exemplary embodiments provided here; changes and modifications may be applied to said embodiments without limiting or departing from the generally intended scope. These and various other adaptations and combinations of the embodiments provided here are within the scope of the disclosed subject matter as defined by the claims and their full set of equivalents. Like numbers refer to like elements throughout.
[0018] The present invention relates to a piston with a cooling gallery having oil retaining plates for internal combustion engine, which is filled with adequate oil for cooling of the piston. The cooling gallery with the oil retaining plates is capable of retaining oil for sufficient time to provide cooling of the piston. The present invention is reliable, light weight and cost-efficient, for heavy duty high specific output and ultra-low emission internal combustion engines.

[0019] FIG. 1 illustrates a cross-sectional view along a thrust axis of a piston (100), in accordance with an exemplary embodiment of the present invention. In general, the piston (100) is a component of an internal combustion engine. Together with a connecting rod and a crankshaft, it forms the crank mechanism of the engine. The main function of the piston (100) is to transform the pressure generated by the burning air-fuel mixture into force, acting on the crankshaft. The piston (100) comprises a body portion (40) that includes a crown portion (10) and a cooling gallery (24) extending along the crown portion (10).The body portion (40) has a combustion chamber (12) configured for direct exposure to combustion gases. The crown portion (10) comes in direct contact with the burning gases, within the combustion chamber (12), so it’s exposed to high thermal and mechanical stress.
[0020] In a preferred embodiment, the piston (100) is made from any material that is able to withstand the elevated temperatures of the engine combustion chamber (12), such as, but not limited to steel, based on design consideration. The steel piston of the present invention is formed from single piece of steel material forged or cast parts which are subsequently subjected to machining and metal working processes. The one-piece steel pistons includes the cooling gallery (24) which may be partially formed during the forging or casting process and which are completely formed after the subsequent machining and metal working. The cooling gallery (24) extends along an inner surface of the crown portion (10).
[0021] The piston body portion (40) further includes a ring belt region (14) immediately adjacent to the combustion chamber (12). The ring belt region (14) includes one or more piston ring grooves (16) configured for receipt of corresponding piston rings (not shown). In the exemplary embodiment, the ring grooves (16) include top most ring groove (11) for receiving a compression ring (not shown), an intermediate ring groove (13) disposed below the topmost ring groove (11) for receiving a scraper ring (not shown) and a bottommost ring groove (15) disposed below the intermediate ring groove (13) for receiving a lowermost oil ring (not

shown). The piston body (40) has a pair of pin bosses (18) from the crown portion (10) extending circumferentially about the center axis to provide laterally spaced pin bores (20) coaxially aligned along a pin bore axis for receiving a wrist pin (not shown).A connecting rod (not shown) is attached to the piston (100) by the wrist pin.
[0022] FIG. 2 illustrates a cross-sectional view of the piston along the pin axis(100) having the cooling gallery (24) with a pair of annular semi-circular retaining plates (28, 29)which can retain oil for sufficient time to provide cooling of the piston (100), in accordance with an exemplary embodiment of the present invention. Note that in FIGS. 1-5, identical or similar parts or components are generally indicated by identical reference numerals. The cooling gallery (24) is located between the ring belt region (14) and the combustion chamber (12) on a bottom surface of a piston head (26). The cooling gallery (24) is formed within the piston body (40)and the crown portion (10). The cooling gallery (14) includes an interior volume located within the piston crown portion (10) adjacent to the ring belt region (14).
[0023] The cooling gallery (24) may generally facilitate cooling of the piston (100). The cooling gallery (24) directs fluid, e.g., engine oil, into the piston crown portion(10). This oil cools the inside walls of the cooling gallery (24) as a result of the rapid reciprocating motion typical of pistons for internal combustion engines during operation. The high-speed collision of engine oil on the surface of the cooling gallery (24) enhance the heat transfer capacity due to cocktail action from the reciprocation of the piston (100).The piston (100) with the cooling gallery (24) further includes the annular semi-circular retaining plates (28, 29) with an inlet gap (30) and an outlet gap (32). The two annular semi-circular retaining plates (28, 29) are positioned at a bottom side (25) of the cooling gallery (24) and at back of the ring belt region (14) to close the cooling gallery (24).
[0024] FIG. 3 illustrate a perspective view of the pair of annular semicircular retaining plates (28, 29), in accordance with an exemplary embodiment of the present invention. The inner surface of the retaining plates (28, 29) is anchored to the cooling

gallery (14) and an outer surface of the retaining plates (28, 29) is welded to the cooling gallery (14) in such a way to retain oil for sufficient time. The inlet gap (30) and the outlet gap (32) of the retaining plates (28, 29) are positioned diametrically opposite to each other with respect to the piston (100). Note that the embodiments discussed herein should not be construed in any limited sense. It can be appreciated that such embodiments reveal details of the structure of a preferred form necessary for a better understanding of the invention and may be subject to change by skilled persons within the scope of the invention without departing from the concept thereof.
[0025] In a preferred embodiment, the two annular semicircular retaining plates (28, 29) is made from any material that is able to withstand the elevated temperatures of the engine combustion chamber (12), such as, but not limited to steel, based on design consideration. The inlet gap (30) is intended to provide direct entry of oil to cooling gallery (24) for introducing a continuous flow or stream of oil from a crank sump supply source (e.g.Cooling jet). It should be recognized that the cooling oil is provided through a piston cooling nozzle arrangement from the crank case appropriately positioned so that the oil enters the cooling gallery (24) via the inlet gap (30) and exits the oil cooling gallery (24) via the outlet gap and returns to the sump. (32). The retaining plates (28, 29) facilitate the continual flow of oil throughout the cooling gallery (24) during reciprocation of the piston (100).
[0026] FIG. 4 illustrates a detailed view of the cooling gallery (24) with the retaining plates(28, 29), in accordance with an exemplary embodiment of the present invention. The inner surface of the retaining plates (28, 29) are anchored to the cooling gallery (24) in a groove (34) and supported in a step machined at back side of the ring belt region (14) as shown by arrow (42). The outer surface of the retaining plates (28, 29) are welded to the cooling gallery (24)to the step machined at back side of the ring belt region (14) as shown by arrow (44). Before welding, the gap between the two semicircular annular retaining plates(28, 29)are positioned in such a way as to provide a passage for oil jet to enter the cooling gallery (24) and exit through diametrically opposite side between the plates(28, 29) via the inlet gap (30) and the outlet gap (32) respectively. The retaining plates (28, 29) provide passage for oil jet to

enter the cooling gallery (24) via the inlet gap (30), retain and circulate the oil to reduce surface temperature of the piston (100) and exit through via the outlet gap (32).The oil cooling gallery (24) may be shaped as desired based on design consideration.
[0027] FIG. 5 illustrates a sectional view of the piston (100) looking from open end towards underside of the crown portion (10), in accordance with an exemplary embodiment of the present invention. The single piece steel piston (100) with the cooling gallery (24) is closed by two semicircular retaining plates (28, 29)with gaps that provide inlet and outlet passage for oil. The semicircular annular retaining plates (28, 29) are firmly attached by anchoring at the inner periphery and laser welding or any other suitable welding process at the outer region to ensure retention of oil for sufficient length of time to provide adequate cooling. In view of the above, it should be recognized that the oil flows directly and efficiently within the cooling gallery (24) to the areas of the piston (100) in need of cooling. As such, the annular semicircular retaining plates (28, 29), allows oil to be retained in the upper region of the cooling gallery (24) in the areas in most need of cooling for an extended period of time, thereby continuously removing heat from these regions.
[0028] The oil is pumped to the cooling gallery (24) via the inlet gap (30) and retains inside the cooling gallery (24) for sufficient time to provide cooling of the piston. The gap (30, 32) between the retaining plates (28, 29) provide passage for oil jet to enter the cooling gallery (24) and exit through diametrically opposite side between the plates (28, 29).The cooling gallery (24) of the single piece steel piston (100) is filled with adequate oil to provide cooling of the piston (100). The piston (100) is adapted for use in light, modern, high performance vehicle engine applications. The present invention is cost effective, reliable and light weight piston solutions for heavy duty high specific output and ultra-low emission internal combustion engines.

[0029] It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

We Claim:
1. A piston (100) for an internal combustion engine, comprising:
a crown portion (10) having an upper combustion chamber (12) and a ring belt region (14) with a plurality of ring grooves (16);
a pair of pin bosses (18) from the crown portion(10) having a pin bore (20) for supporting a wrist pin;
a cooling gallery (24) located between the ring belt region (14) and the combustion chamber (12) on a bottom surface of a piston head (26); and
a pair of semi-circular retaining plates (28, 29) with an inlet gap (30) and an outlet gap (32) positioned at a bottom side (25) of the cooling gallery (24) and at back side of the ring belt region (14) to close the cooling gallery (24),
wherein the retaining plates (28, 29) provide passage for an oil jet to enter the cooling gallery (24) via the inlet gap (30), retain and circulate the oil to reduce surface temperature of the piston (100) and exit through via the outlet gap (32).
2. The piston (100) of claim 1, wherein an inner surface of the retaining plates (28, 29) area anchored to the cooling gallery (24) in a groove (34) at back side of the ring belt region (14) and an outer surface of the retaining plates (28, 29) are welded to the cooling gallery (24) at back side of the ring belt region (14).
3. The piston (100) of claim 1, wherein the inlet gap (30) and the outlet gap (32) of the retaining plates (28, 29) are positioned diametrically opposite to each other with respect to the piston (100).
4. The piston (100) of claim 1, where in inlet gap (30) provides passage of oil to the gallery (24) by means of a continuous flow or stream of oil from a crank sump supply source and retains inside the cooling gallery (24) for sufficient time to provide cooling of the piston.

5. The piston (100) of claim 1, wherein the piston (100) is formed from a single piece of steel material.
6. The piston (100) of claim 1, wherein the two semi-circular retaining plates (28, 29) are made from a steel material.