The present invention relates to internal combustion engines, and more particularly to systems and methods for detecting continuous reverse rotation of an internal combustion engine.
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.
It is unlikely that a conventional engine will rotate in reverse for a long period 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.
Accordingly, a reverse rotation detection system for an engine with at least one camshaft and a crankshaft includes a camshaft position sensor that generates a camshaft position signal based on a rotation of the camshaft. A second sensor input device generates a crankshaft position signal based on a rotation of the crankshaft. A control module detects a reverse rotation condition of the engine from the camshaft position signal and the crankshaft position signal, wherein the control module compares the camshaft position signal to the crankshaft position signal to determine an engine position. Based on the engine position the control module compares the camshaft position signal to an expected signal to determine a reverse rotation condition.
In one other feature, if the engine position indicates that the camshaft is retarded relative to the crankshaft, the expected signal is selectable for a crankshaft region. The region is defined by a first crankshaft angle and a second crankshaft angle referenced relative to top dead center of a cylinder of the engine. The control module compares an edge of the camshaft position signal to an edge of the expected signal.
In other features, if the engine position indicates that the camshaft and the crankshaft are synchronized, the expected signal is the camshaft position signal at a region of the camshaft stored during a previous rotation of the crankshaft. The region is defined by a first camshaft angle and a second camshaft angle. The control module compares a state of the camshaft position signal to a state of the expected signal.
In still other features, the system includes a wheel coupled to the camshaft having a plurality of teeth, wherein the camshaft position sensor generates the camshaft sensor signal based on the plurality of teeth of the wheel. The system can also include a wheel coupled to the crankshaft having a plurality of teeth, wherein the crankshaft position sensor generates the crankshaft position signal based on the plurality of teeth of the wheel.
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 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 similar 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 (not shown) 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 (not shown) to produce drive torque. Combustion exhaust within the cylinder 18 is forced out through an exhaust manifold 28 when an exhaust valve 30 is in an open position. The exhaust valve position is regulated by an exhaust camshaft 32. The exhaust is treated in an exhaust system. Although single intake and exhaust valves 22,30 are illustrated, it can be appreciated that the engine 12 can include multiple intake and exhaust valves 22,30 per cylinder 18.
The engine system 10 can include an intake cam phaser 34 and/or an exhaust cam phaser 36 that respectively regulate the rotational timing of the intake and exhaust camshafts 24,32. More specifically, the timing or phase angle of the respective intake and exhaust camshafts 24,32 can be retarded or advanced with respect to each other or with respect to a location of the piston within the cylinder 18 or crankshaft position. In this manner, the position of the intake and exhaust valves 22,30 can be regulated with respect to each other or with respect to a location of the piston within the cylinder 18. By regulating the position of the intake valve 22 and the exhaust valve 30, the quantity of air/fuel mixture ingested into the cylinder 18 and therefore the engine torque is regulated. A control module 40 controls the phase angle of the intake cam phaser 34 and exhaust cam phaser 36 based on a desired torque.
Referring now to
Similarly, a wheel sensor 60 senses the teeth of a wheel 62 coupled to the exhaust camshaft 32 (
Referring now to
In step 100, the wheel sensors sense the position of the camshaft and the crankshaft. The position of the camshaft is determined relative to the position of the crankshaft. The camshaft and the crankshaft are synchronized if their states match a pre-selected pattern, and the engine has sustained it's own forward rotation as measured by crankshaft speed. If the camshaft and crankshaft 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. 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 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 is rotating in a reverse direction at step 140.
Referring back to step 110, otherwise, if the camshaft and crankshaft 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 referenced relative to top dead center of a cylinder. The reference cylinder 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 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 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
According to the present invention, an engine position is determined from a crankshaft signal and a camshaft signal. When the crankshaft and camshaft are synchronized, the cam sensor signal can be evaluated twice per one revolution of the crankshaft to determine the rotation of the engine. For example, regions shown at 280 and 282 define when the cam sensor signal can be evaluated for a 58× crank 4× cam sensing strategy. Regions 280 and 282 correspond to cam angle regions where the decoded forward teeth numbers of the crankshaft wheel are 18–20 and 46–51 respectively. The same regions are also defined by decoded reverse teeth numbers 39–41 and 8–12 respectively. The camshaft sensor signal state is compared to the previous camshaft sensor signal state for these regions 280 and 282 to determine if the engine is rotating in reverse. If the cam sensor signal state does not match the previous cam sensor signal state, the engine is rotating in reverse.
If the crankshaft and camshaft are not synchronized, the edges of the cam sensor signal can be evaluated at a selectable region defined by a crank angle in degrees relative to TDC for a cylinder. In the current example, the selectable region can be between 138 degrees and 150 degrees shown at 283. Within this region, the edges of the cam sensor signal are compared against an edge of an expected cam sensor signal. The expected edge can be selectable based on an angle of the crankshaft relative to top dead center of a cylinder. If the edge matches an expected edge for reverse rotation, the engine is rotating in reverse.
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.
Number | Name | Date | Kind |
---|---|---|---|
4491122 | Piteo | Jan 1985 | A |
4909229 | Hashizume | Mar 1990 | A |
5604304 | Kokubo et al. | Feb 1997 | A |
6732713 | Kanazawa et al. | May 2004 | B1 |
7017556 | Borg et al. | Mar 2006 | B2 |
7047956 | Masaoka et al. | May 2006 | B2 |