Piston with blow-by feature and method of preventing catastrophic failure to an internal combustion engine

A piston and method is provided that inhibits the potential catastrophic damage to an internal combustion engine, thereby reducing the risk of costly damage to the engine. The piston includes a piston body having an upper combustion surface separated from an internal cooling chamber by a wall. The a pocket extends into the upper combustion surface to a closed bottom surface of the wall. A tubular member is disposed in the pocket. The tubular member extends upwardly from the upper surface. Should a valve head drop from its normal operating position, the valve head impacts the tubular member and forms a blow-by through passage extending from the upper combustion surface into the cooling chamber.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to internal combustion engines, and more particularly to pistons therefor.

2. Related Art

A known potential failure mode of an internal combustion engine results when a valve drops into contact with the piston during operation, which can result in catastrophic failure of the engine. The damage resulting to the engine can include replacement of the entire power cylinder system (piston, rings, liner, wrist pin, connecting rod), valve train, cylinder head, crankshaft, and many times, the engine block. Accordingly, although repairable, the cost to repair a failure mode of this nature can be very expensive.

SUMMARY OF THE INVENTION

A piston is provided that inhibits the potential catastrophic damage to an internal combustion engine, thereby reducing the risk of costly damage to the engine. The piston includes a piston body having an upper surface separated from an internal cooling chamber by a wall. The upper surface has a pocket extending to a closed bottom surface of the wall. A tubular member is disposed in the pocket. The tubular member extends upwardly from the upper surface.

In accordance with another aspect of the invention, a method of preventing catastrophic failure to an internal combustion engine is provided. The method includes providing a piston body having an upper surface separated from an internal cooling chamber by a wall. And, providing predetermined locations in the wall underneath valve heads for a through opening to be formed through the wall into the internal cooling chamber in use.

In accordance with another aspect of the method, the method further includes forming a pocket extending into the upper surface to a closed bottom surface of the wall and disposing a tubular member in the pocket with the tubular member extending upwardly from the upper surface.

In accordance with another aspect of the invention, a method of preventing catastrophic failure to an internal combustion engine is provided by providing a predetermined location in a upper wall of a piston for a valve head to impact to form a blow-by passage extending into an internal cooling chamber of the piston. The blow-by passage provides a sudden increase in blow-by, thereby providing an immediate indication of a problem. The indication is utilized to prevent further damage from resulting to the engine.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS

Referring in more detail to the drawings,FIG. 1illustrates a piston10constructed in accordance with one presently preferred aspect of the invention. The piston10has a piston body12extending along a central axis14along which the piston10reciprocates within a cylinder bore (not shown). The piston body12, by way of example and without limitation, includes an upper crown portion16having an upper combustion surface18, represented here, by way of example and without limitation, as having an annular, planar, radially outer portion20and a recessed combustion bowl22radially inwardly from the outer portion20. The outer portion20is configured to be aligned beneath a plurality of valve heads23(FIG. 1A). The piston10is shown as having internal outer and central cooling galleries or chambers24,26, respectively, separated from one another by an annular inner rib28, by way of example and without limitation, with an annular outer rib29depending from the outer portion20. The upper combustion surface18is separated from the outer and inner cooling galleries24,26by an upper wall30. At least one pocket, and preferably a number of pockets32corresponding with the number valve heads, shown as4inFIG. 1A, by way of example and without limitation, extends into the upper combustion surface18of the wall30over a depth (D) to a closed bottom surface34of the wall30. A tubular member36is disposed in each one of the pockets32into abutment with the closed bottom surface34. Upon being disposed into abutment with the bottom surface34, or very close proximity thereto, the tubular member36extends upwardly from the upper combustion surface18. Accordingly, should any one of the valve heads23become loose and drop from its normal functioning position, the respective valve head23impacts the underlying tubular member36, thereby causing the tubular member36to impact the frangible closed bottom surface34with sufficient force to break through the frangible closed bottom surface34, as shown inFIG. 3. As such, an intended orifice, also referred to as through passage or blow-by passage38, is formed in a predetermined location through the upper wall30. The blow-by passage38provides a sudden increase in gas/fuel mixture blow-by, thereby providing an immediate indication, such as can be detected by a pressure sensor sensing pressure within the cylinder bore, for example, of a problem. The indication of the sudden pressure change can be signaled to an operator or to an engine control system, thereby allowing the operator or the engine control system to shut down the engine to avoid further damage to the engine.

As shown inFIG. 1, the piston10can be constructed having, by way of example and without limitation, a lower crown portion40with a lower inner rib42and lower outer rib44arranged in axial alignment for fixed attachment with the upper inner and outer ribs28,29to form the outer and inner cooling galleries24,26. A pair of pin bosses46depend from the upper crown portion16to provide a pair of wrist pin bores48aligned along a pin axis50for receipt of a wrist pin (not shown). A space51is provided between the pin bosses46for receipt of a small end of a connecting rod (not shown). It should be recognized that the cooling galleries24,26could be formed other than as discussed and shown, and that rather than having dual galleries, a single cooling gallery could be provided.

Each pocket32extends over the depth (D) extending from the upper combustion surface18to the closed bottom surface34. The pockets32can be formed having a smooth inner wall52or they could be formed having a textured, knurled or threaded portion53(FIG. 2A), depending on the desired mechanism used to fix the tubular member36therein. The threaded portion53is shown as extending over about the upper half of the pocket32, wherein the lower half remains unthreaded, for example. As such, the threads53provide sufficient retention of the tubular member32for normal operating conditions, while allowing the tubular member32to be driven downwardly under the impact of the overlying valve head23. Accordingly, with only a portion of the pocket32being threaded, the tubular member is assured of being driven into the underlying cooling gallery24upon being impacted by the overlying valve head23should the valve head23drop from its normal functioning position. The inner wall52is preferably formed having a straight, cylindrical shape, for ease of manufacture, though, if desired, other shapes could be used. The pocket32provides a reduced thickness portion54of the wall30, wherein the reduced thickness portion54has a predetermined thickness (t) extending between the bottom surface34of the pocket32and an underside55.

The tubular member36has an outer surface56, shown as being a straight, cylindrical surface, for example, configured for fixed receipt in the pocket32. Accordingly, if inner wall52of the pocket32is smooth or substantially smooth, then the outer surface56can be sized for a tight fit, also referred to as press fit, in the pocket32. Otherwise, an adhesive or mechanical attachment mechanism could be used to fix the tubular member36in the pocket32, with the premise that the adhesion or mechanical attachment mechanism be selectively broken should the valve head23impact the tubular member36. Further, if the inner wall52has a threaded portion (FIG. 2A), then the outer surface56of the tubular member36could likewise have a mating thread portion for threaded attachment in the pocket32. Upon being fixed in the pocket32, regardless of how, e.g. pressed tight fit, adhered, threaded, or otherwise, a bottom end58of the tubular member36is brought into abutment with or very close proximity to the bottom surface34of the pocket32and an upper end60of the tubular member36extends upwardly from the upper surface18, shown here as extending upwardly from the planar outer portion20. As such, the tubular member36is constructed having a predetermined length (l) that is greater than the depth D of the pocket32such that the upper end60is assured of extending upwardly above the upper combustion surface18of the outer portion20a predetermined distance (d) when the bottom surface58is abutting the bottom surface34of the pocket32. The distance d is provided to be the at least the same as or slightly greater than the thickness t of the reduced thickness portion54of the wall30. It should be understood that the upper end60does not interfere with the overlying, axially aligned valve head23or otherwise have an adverse affect on the performance of the engine during normal operating conditions.

If the overlying valve head23is lowered into the cylinder bore combustion chamber from its normal operating position (malfunction condition of the valve head23) such that it abuts the upper end60of the underlying tubular member36, the force generated drives the tubular member36downwardly into the pocket32and the reduced thickness, frangible portion54of the wall30is caused to be fractured under the driving force of the tubular member36. As such, the tubular member36extends completely between the upper combustion surface18and the internal outer cooling gallery24to form the blow-by passage38(FIG. 3). The blow-by passage38is assured of being formed as a result of the dimensional relation between the wall thickness t and the distance d by which the tubular member36extends above the upper surface20. At a minimum, when the upper end60of the tubular member36is brought flush, or substantially flush with the outer surface20as a result of being driven downwardly by the valve head23, the bottom end58of the tubular member36is driven flush with or into the outer cooling gallery24. Accordingly, the through passage extending through the tubular member36extends completely from the upper combustion surface18into the outer cooling gallery24, thereby providing the open blow-by passage38. As such, when this occurs, the amount of gas/fuel mixture blow-by increases given the gas/fuel mixture is free to flow through the through passage38into the cooling gallery24, thereby promoting a loss or decrease of pressure signal to be sent to the operator and/or to a control unit, and in turn, allowing the operator and/or control unit to shut down the engine before the onset of further damage to the engine.