Patent Application
20070163556
The present invention relates to internal combustion engines, and more particularly to systems and methods for protecting an intake manifold during reverse engine rotation.
An internal combustion engine generally operates in four modes; an intake mode, a compression mode, a combustion mode and an exhaust mode. During reverse rotation of an engine, the engine cycle executes in a reverse order whereby the compression mode is followed by the intake mode. For example, when an engine that is stopped begins to start again, the engine may have a cylinder that was in a compression mode at the moment of stopping. Compression pressure in the cylinder may push a piston in reverse toward bottom dead center (BDC). When engine speed increases, a cylinder with injected fuel may experience ignition and the reverse rotation may be accelerated.
Conventional engines will rarely rotate in reverse for long periods of time. Torque control systems are capable of limiting the duration of the reverse rotation. However, the problem arises more frequently in hybrid electric propulsion systems. An external force (such as an electric motor) can rotate the internal combustion engine in reverse for longer durations at higher speeds. Conventional torque control systems are not able to control torque under these conditions.
If reverse rotation occurs, engine components such as the intake manifold can be damaged. Reverse rotation may cause a compressed air/fuel mixture to flow back into the intake manifold during the intake stroke through an open intake valve. Pressure in the intake manifold increases. If further reverse rotation occurs, pressure may increase further and cause damage to the intake manifold.
In addition to damage to the intake manifold, reverse rotation of the engine may cause further problems such as excess bearing wear and damage to gaskets, hoses and sensors connected to the intake manifold.
A method of protecting an intake manifold of an engine of a hybrid propulsion system including an electric motor comprises detecting a reverse rotation of an engine. A fuel injector of the engine that is rotating in reverse is commanded to cease operation. A spark plug of the engine that is rotating in reverse is commanded to cease operation. The ceasing of reverse rotation of the engine is then confirmed.
In another feature, the method comprises notifying a diagnostic module of the reverse rotation.
In another feature, an electric motor is commanded to cease operation after detecting reverse rotation is performed, wherein commanding the electric motor to cease operation further comprises commanding the electric motor to begin forward rotation.
In another feature, the method comprises commanding the fuel injector to re-enable and commanding the spark plug to re-enable after confirming of the ceasing of reverse rotation of the engine is performed.
In other features, detecting reverse rotation comprises comparing an actual cam sensor signal to an expected cam sensor signal. Wherein the expected cam sensor signal is determined based on the actual cam sensor signal and a crankshaft sensor signal.
In other features, the expected cam sensor signal is set to a previously stored actual cam sensor signal, and wherein detecting reverse rotation further comprises comparing a state of the actual cam sensor signal to a state of the expected cam sensor signal while the engine is operating in at least one of a first region and a second region and when a camshaft and crankshaft are synchronized.
In still other features, the expected cam sensor signal is set to an expected reverse cam sensor signal, and wherein detecting reverse rotation further comprises comparing an edge of the actual cam sensor signal to an edge of the expected cam sensor signal for a selected crank angle region relative to top dead center of a specified cylinder when a camshaft and crankshaft are not synchronized.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify the same elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
Referring now to
A fuel injector 20 injects fuel that is combined with the air as it is drawn into the cylinder 18 through an intake port. An intake valve 22 selectively opens and closes to enable the air/fuel mixture to enter the cylinder 18. The intake valve position is regulated by an intake camshaft 24. A piston (not shown) compresses the air/fuel mixture within the cylinder 18. A spark plug 26 initiates combustion of the air/fuel mixture, driving the piston in the cylinder 18. The piston drives a crankshaft 28 to produce drive torque.
Combustion exhaust within the cylinder 18 is forced out through an exhaust manifold 30 when an exhaust valve 32 is in an open position. The exhaust valve position is regulated by an exhaust camshaft 34. The exhaust is treated in an exhaust system (not shown). Although single intake and exhaust valves 22,32 are illustrated, it can be appreciated that the engine 12 can include multiple intake and exhaust valves 22,32 per cylinder 18. An electric motor 36 provides an alternate source of power needed to rotate the crankshaft 28 of the engine 12. A control module 38 senses inputs from the engine system and responds by controlling the aforementioned components of the propulsion system 10.
Control module 38 can determine when the engine 12 is operating in reverse rotation by evaluating a pulse train signal generated by a cam sensor 40 and a pulse train generated by a crankshaft sensor 41. Referring now to
In step 100, the sensors sense the position of the camshaft 24 and the crankshaft 28. The. position of the camshaft 24 is determined relative to the position of the crankshaft 28. The camshaft and the crankshaft are synchronized if their states match a preselected pattern, and the engine has sustained it's own forward rotation as measured by crankshaft speed. If the camshaft 24 and crankshaft 28 are synchronized in step 110, a state of the camshaft signal is evaluated in step 120 for a selectable region defined by a first and a second angle of the camshaft 24. The state of the signal can be either high or low. In step 120, if an actual cam signal state matches a cam signal state previously sensed at the selectable region, the engine 12 is rotating in a forward direction at step 130. Otherwise if an actual cam signal state does not match a cam signal state previously sensed at the selectable region, the engine 12 is rotating in a reverse direction at step 140.
Referring back to step 110, otherwise, if the camshaft 24 and crankshaft 28 are not synchronized, in steps 150 and 160 an edge of the camshaft sensor signal is evaluated at a region defined by a first and a second angle of the crankshaft position referenced relative to top dead center of a cylinder 18. The reference cylinder 18 can be selectable. The signal edge can be either low to high or high to low. In step 150, if an actual camshaft signal edge matches an expected reverse camshaft signal edge for that region, the engine 12 is rotating in a reverse direction at step 140. Otherwise, in step 160, if an actual camshaft signal edge matches an expected forward camshaft signal edge for that region, the engine is rotating in a forward direction at step 130. Otherwise, the rotation of the engine 12 is indeterminate at step 170. The expected forward camshaft signal edge and the expected reversed camshaft signal edge can be selectable according to an angle of the camshaft.
Referring now to
Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.
