The present invention relates generally to engine synchronization, and more particularly to a method of identifying the crankshaft phase from the camshaft location resulting in engine synchronization at a reduced time.
Generally in a conventional four stroke engine, an electric engine controller must determine the angular position of the engine by processing signals from sensors on the cam and crank shafts. The four stroke engine cycle repeats every two revolutions of the crankshaft or 720 degrees of crankshaft rotation. The crankshaft signal however, repeats every 360 degrees of crankshaft rotation. The camshaft rotates at half speed of the crankshaft, therefore the camshaft signal repeats every 720 degrees of engine rotation. Information from the camshaft is required to determine which half (or phase) of the 720 degree cycle the crankshaft is in. Normally the crankshaft signal is used to control the engine because of its higher accuracy and the camshaft is used only as a phase reference.
To start the engine quickly, synchronization must be achieved as soon as possible. The crankshaft has reference points every 180 degrees allowing the crankshaft position to be determined around 210 degrees. However the phase is not known based on the crank alone, therefore the engine position can be x or x+360 degrees. The phase cannot be determined until the engine position is determined uniquely from the camshaft signal. The camshaft has fewer teeth to generate a signal from, therefore more engine rotation is needed to achieve synchronization on the camshaft signal. A method is needed to exploit information available from the camshaft signal in order to reduce the overall synchronization time.
According to a preferred embodiment of the present invention, a method for determining the angular position of an internal combustion engine throughout an engine cycle is provided. The method includes the steps of providing a crankshaft having a plurality of teeth, the crankshaft completing two revolutions per engine cycle. A camshaft is provided having a plurality of teeth, the camshaft completing one revolution per engine cycle. An engine controller is also provided. A sample size of an engine cycle is designated in each of two concurrent engine cycles. The teeth are counted which appear on the camshaft in the sample sizes. The crankshaft position is determined according to the teeth appearing in the sample sizes.
Further areas of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.