Thin profile cam sprocket with integrated timing target

Details Thin profile cam sprocket with integrated timing target Thin profile cam sprocket with integrated timing target

1999-12-08

2001-08-21

Bucci, David A. (Department: 3682)

Endless belt power transmission systems or components

Positive drive pulley or guide roll

C474S160000, C474S156000

Reexamination Certificate

active

06277045

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a timing assembly for an internal combustion engine. More specifically, this invention relates to a camshaft sprocket for use with a position sensor to indicate the angular position of a camshaft.
2. Description of the Prior Art
A typical internal combustion engine has an engine block with a plurality of cylinders each having a reciprocally movable piston disposed therein which defines a combustion chamber. The engine block supports a crankshaft interconnected by connecting rods to the pistons so that as the pistons move linearly within the cylinders they produce rotation of the crankshaft. The engine also includes at least one camshaft which is supported so as to actuate valves that control flow of air, fuel and exhaust to and from the combustion chambers. Sprockets are attached to the ends of the crankshaft and the camshaft(s) and a timing belt or chain interconnects the crankshaft to the camshaft(s). The diameter of the crankshaft sprocket is half the diameter of the camshaft sprocket so that for every two full rotations of the crankshaft the camshaft rotates once. The timing belt or chain ensures that the camshaft rotates properly to actuate the valves at the appropriate time in relation to the position of the pistons.
Modern engines utilize computer control and various sensors to control engine functions such as ignition timing and fuel injection operation. These sensors relay information to the computer for processing and then transmitting commands to the devices to control various aspects of engine operation, such as fuel injection and ignition park timing. Typically, the computer coordinates these devices by referencing the position of a particular piston, or triggering piston, specifically when it attains a top dead center position within its cylinder (TDC). The timing of the engine in relation to the piston's position is critical in maintaining efficient engine operation and controlling engine emissions.
Many types of sensors for computer control have been employed to track the angular position of an engine crankshaft and camshaft(s) for timing purposes. Specifically, sensors have been employed to detect the position of the camshaft sprocket attached to one end of the camshaft, which position correlates to the position of the piston because of its connection to the crankshaft by the timing belt or chain. However, this configuration has proven to be problematic from a packaging standpoint due to the very limited space constraints of a modern engine and its associated vehicle.
SUMMARY OF THE INVENTION AND ADVANTAGES
The present invention provides a timing assembly for use with an internal combustion engine. The engine has a shaft support structure for a camshaft and provides a timing assembly at an end of the camshaft which has an axis of rotation. A camshaft sprocket is attached to the one end of the camshaft coaxially therewith and has radially extending teeth thereon. The sprocket has a first end surface extending perpendicularly to the camshaft's axis of rotation. A position sensor, preferably a Hall effect type sensor, is attached to the camshaft support structure adjacent to the first surface. An annular timing surface configuration is located on the first surface and is spaced radially from the axis of rotation. The annular timing surface configuration includes a first arcuate region extending outwardly from the first surface and a second arcuate region recessed with respect to the first region. This produces a step between the two regions. Another way to produce a step would be by providing a projection or a recessed portion. The annular timing surface configuration is axially spaced from the position sensor such that the sensor detects the angular position of the sprocket when the step region is encountered. This detecting of the step between the first and second arcuate regions corresponds to the TDC of the triggering piston. The complex shape of the integral camshaft sprocket and sensor reading surface configuration is preferably formed of powdered metal. Utilizing this process permits placement of apertures in the sprocket for balancing purposes.
Accordingly, the present invention provides a one-piece, thin profile camshaft sprocket that is easily packaged in tight spaces. Further, the sprocket is light weight and well balanced while providing an effective timing surface configuration for a position sensor to generate a desired signal.


REFERENCES:
patent: 3103209 (1963-09-01), Bekkala et al.
patent: 4457269 (1984-07-01), Beardmore
patent: 5209202 (1993-05-01), Maurer et al.
patent: 6090320 (2000-07-01), Grundner et al.
patent: 6138623 (2000-10-01), Heer

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