Engine Stroke Determination via Intake Pressure Waveform Analysis
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Solution Overview
Problem
Conventional stroke determination methods in 4-cycle engines are time-consuming and prone to electrical noise interference, especially when comparing intake pressure magnitudes across varying engine speeds, making accurate and efficient stroke determination challenging.
Innovation Solution
A stroke determination unit and method that utilize a crankshaft sensor and intake pressure variation generating device to recognize patterns in combined intake pressure waveforms within specified crankshaft phases, reducing noise interference and computing load, and allowing for accurate stroke determination across different engine speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stroke determination is carried out based on magnitude relationship of intake pressures across all engine speed regions, then comprehensive stroke determination is achieved, but determination time becomes excessively long
Solution Approach 1:
The patent segments the stroke determination process by engine speed regions. It divides the determination into a first determination for low-speed regions (below predetermined RPM) and a second determination for high-speed regions (above predetermined RPM). This segmentation allows each determination to use optimized methods suitable for its speed range, reducing overall determination time while maintaining accuracy across all regions.
Solution Approach 2:
The patent dynamically selects the determination method based on engine speed. When engine speed exceeds the predetermined value, it switches from the first determination method to the second determination method. This dynamic adaptation allows the system to use the most efficient method for the current operating condition, resolving the contradiction between comprehensive determination and time efficiency.
2Device complexity
If stroke determination is based on comparing intake pressure magnitudes at particular points, then determination is simplified, but noise suppression becomes difficult
Solution Approach 1:
The patent transitions from one-dimensional point-based pressure comparison to two-dimensional waveform analysis. By analyzing the entire intake pressure waveform pattern across multiple crankshaft phases rather than comparing single-point magnitudes, the system gains additional dimensional information that enables both simplified determination logic and improved noise suppression through pattern recognition.
Solution Approach 2:
The patent performs preliminary waveform combination before determination. It pre-combines intake pressure waveforms from multiple cylinders to create a composite waveform pattern, then uses this pre-processed pattern for stroke determination. This preliminary action simplifies the subsequent determination process while the aggregated waveform pattern inherently suppresses noise through averaging effects.
3Measurement precision
If camshaft phase detection is implemented, then accurate stroke determination is achieved, but engine size and weight increase
Solution Approach 1:
The patent extracts and removes the camshaft phase detection requirement from the stroke determination system. By using only crankshaft position information combined with multi-cylinder intake pressure waveform analysis, it eliminates the need for camshaft sensors and associated hardware, thereby reducing engine weight and complexity while maintaining determination accuracy.
Solution Approach 2:
The patent makes the crankshaft position sensor and intake pressure sensors serve multiple functions. These components are used not only for their primary purposes but also for stroke determination, eliminating the need for dedicated camshaft phase detection hardware and reducing overall system weight.
Data Source
AI summary
A stroke determination unit for a 4-cycle engine uses intake pressure as a parameter to provide accurate stroke determination. A combined pressure combines the detected pressures of intake ports of the first to third cylinders, and stroke determination is carried out by recognizing, within a combined pressure waveform based on a detection value for the combined pressure, shapes of the combined pressure waveform for a specified phase period of a crankshaft. The pressure pattern recognition is carried out by storing variation patterns of pressure values measured within the specified crankshaft phase period, and collating patterns with a data map stored within an ECU. Alternatively, the pattern recognition is carried out by collating with condition equations representing “rising” or “upward peak”. With the latter, pressure variation due to contamination such as electrical noise to the pressure sensor is made negligible, and noise suppression of the stroke determination unit is improved.