1. Field of the Invention
This invention relates to a rotational position sensor device used for an internal combustion engine for detecting the rotational position thereof for ignition timing control or the like.
2. Description of the Prior Art
FIG. 4 is a sectional view showing a prior art internal combustion engine rotational position sensor device disclosed in Japanese Utility Model Publication Sho 60-23,714. In the figure, reference numeral 1 designates a timing cam pulley, 2 a cam shaft, on which the cam pulley 1 is mounted, 3 a bolt for securing the cam pulley 1 to the cam shaft 2, 4 a belt cover, 6 a rotational position sensor mounted on an engine body, and 7' and 8' annular ribs coaxially provided on an end face of the timing cam pulley 1. The ribs 7' and 8' have slits. When these slits pass by the rotational position sensor 6, the sensor 6 provides a signal corresponding to the rotational position of the cam shaft 2.
In the assembly of the above prior art internal combustion engine rotational position sensor device, the rotational position sensor 6 is first mounted on the engine body, and then the timing cam pulley 1 having the annular ribs 7' and 8' is mounted on the cam shaft 2. Therefore, the overall measurement accuracy of the device depends on the manufacturing accuracy of various components, and cannot be determined until the device has been actually assembled for use. In other words, the performance of the device can neither be confirmed nor ensured until it has been actually assembled for use. Further, when it is disassembled by removing the timing cam pulley 1 and other components and reassembled due to a defect of other components, its accuracy is subject to variations, and it is impossible to ensure a fixed performance.