Common Rail Pressure Plateau Detection for Injection Equalization
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Solution Overview
Problem
Existing methods for determining pressure conditions in a common rail for internal combustion engines face challenges in precision due to reduced selectivity in pressure signals, especially with increased rail pressure and multiple injections, leading to insufficient measuring points for accurate injection quantity equalization, particularly under stricter emissions standards like EURO 7.
Innovation Solution
A method involving stepwise observation of time windows in the pressure signal to determine regression lines, identifying pressure plateaus by a slope threshold, and combining overlapping plateaus for improved accuracy, allowing for precise injection quantity adjustment across cylinders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If rail pressure is increased to up to 500 bar for particulate reduction, then emissions are reduced, but selectivity in the common rail pressure signal decreases
Solution Approach 1:
The pressure signal evaluation is segmented into multiple time windows, with each window focusing on a specific injection event. This segmentation allows the system to extract meaningful pressure plateau information even when the overall signal selectivity is reduced due to high rail pressure and multiple injections per combustion cycle.
Solution Approach 2:
The patent transitions from evaluating the pressure signal in the time domain only to incorporating frequency domain analysis through Fourier transformation. By examining the signal in both time and frequency domains, the system can identify pressure plateaus more reliably despite reduced signal selectivity at high injection pressures.
2Object-generated harmful factors
If multiple injection strategy is expanded with up to ten injections per combustion cycle, then particulate reduction is achieved, but the number of available measuring points decreases
Solution Approach 1:
The system performs preliminary identification of pressure plateaus by analyzing the pressure signal characteristics before proceeding with injection quantity calculations. By pre-identifying valid measurement points through plateau detection in time windows, the system ensures sufficient measuring points are available even with multiple injections per cycle.
Solution Approach 2:
The patent implements a feedback mechanism where the detected pressure plateaus are used to validate and adjust injection quantity calculations. The system continuously monitors whether sufficient plateaus are detected and can adapt the evaluation parameters to ensure adequate measuring points are available for accurate injection equalization.
3Device complexity
If conventional plateau determination methods are used with high rail pressure, then processing is simpler, but injection quantity equalization accuracy becomes insufficient
Solution Approach 1:
The patent introduces dynamic adaptation of evaluation parameters based on the detected signal characteristics. The time window size, threshold values, and other parameters are adjusted dynamically according to the rail pressure level and injection pattern, allowing the system to maintain high measurement precision across different operating conditions without excessive complexity.
Solution Approach 2:
The system changes key evaluation parameters such as time window duration, pressure threshold offsets, and plateau detection sensitivity based on the operating conditions. By adapting these parameters to match the specific rail pressure level and injection strategy, the system achieves accurate injection quantity equalization while managing processing complexity.
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3~4
AI summary
The invention relates to a method (100) for determining pressure states in a common rail (4) for an internal combustion engine (1), comprising retrieving a pressure signal (200) indicating a pressure in the common rail (4); stepwise analysis of time windows in the pressure signal (200), whereby a regression line is determined for each time window; and determining that a pressure plateau (201a-d, 202a-b, 203a-b) exists in one of the time windows if the slope of the regression line is equal to or less than a predetermined slope limit. The present invention further relates to a control unit (9) and a motor vehicle (20).