Cam Top Position Detection in High Pressure Pumps
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Solution Overview
Problem
The conventional high pressure pump for accumulator fuel injection systems requires a significant amount of time to start the engine due to the slow rotation speed of the camshaft, as the cam top position is detected only once per rotation, leading to increased engine start time.
Innovation Solution
A device for detecting the cam top position in an in-line type high pressure pump, where multiple cam lobes on the camshaft or flywheel are equipped with corresponding cam top position pointers, allowing the cam top position detector to capture multiple detection points per rotation, thereby reducing the time interval for engine start operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the cam top position is detected once per rotation of the camshaft, then the detection system is simple, but the engine start time increases due to slow camshaft rotation speed
Solution Approach 1:
The camshaft is divided into multiple cam lobes (typically 3 or 4), and each cam lobe has its own cam top position pointer. The detector detects multiple pointers during one camshaft rotation, segmenting the detection process into multiple simultaneous detection points rather than a single sequential detection, thereby reducing the effective detection time interval.
Solution Approach 2:
The detection system uses periodic cam top position pointers that are equally spaced around the camshaft circumference. As the camshaft rotates, the detector periodically encounters each pointer in sequence during one rotation, creating multiple detection events per rotation cycle. This periodic arrangement allows the system to obtain multiple reference positions within a single rotation period.
2Measurement precision
If multiple cam top position pointers are provided to reduce detection time interval, then the detection precision and speed improve, but the device complexity increases
Solution Approach 1:
The single cam top position detector serves multiple functions by detecting multiple different pointers (one for each cam lobe) during one camshaft rotation. The detector is positioned to face the outer periphery of the camshaft where multiple pointers are arranged, allowing it to sequentially detect each pointer's position relative to the detector, thereby obtaining reference positions for all cam lobes simultaneously in one rotation.
Data Source
AI summary
A device detects the cam top position in an in-line type high pressure pump with a decreased amount of time required to detect the rotation position of the cam top position in an engine starting operation, thereby decreasing the time for starting an engine. A cam for driving a plunger has a plurality of cam lobes, and a plurality of cam top position pointers are attached to the outer periphery of the camshaft or to the outer periphery of a flywheel connected to the camshaft such that each of the pointers corresponds to each of the cam lobes of the cam in number and angle phase, respectively. A cam top position detector is located to face the pointers when the camshaft rotates so that the pointers are detected by the detector.