Engine Blowby Pressure Diagnostic Unit
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Solution Overview
Problem
Existing abnormality diagnostic devices for internal combustion engines face challenges in maintaining accurate diagnosis due to the behavior of pressure in the blowby gas passage.
Innovation Solution
An abnormality diagnostic device that includes a reference value setting unit, an accumulating unit, and a diagnostic unit. The device sets a reference value for pressure in a passage connected to the intake passage of the engine, accumulates a cumulative value by tracking the difference between the reference value and the actual pressure, and diagnoses abnormalities based on this cumulative value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure in the blowby gas passage is used for diagnosis, then abnormality detection is enabled, but diagnosis accuracy decreases due to pressure behavior
Solution Approach 1:
The system performs preliminary actions by accumulating the difference between reference pressure and actual pressure over time before making a diagnosis. The accumulating unit integrates pressure deviations over a predetermined period, allowing the system to account for transient pressure fluctuations and only trigger abnormality detection when cumulative deviations exceed a threshold, thereby improving diagnosis accuracy while maintaining detection capability
Solution Approach 2:
The system implements feedback by continuously comparing actual pressure against reference pressure and accumulating the differences. The diagnostic unit uses this accumulated feedback information to make informed decisions about abnormality detection, adjusting the diagnosis based on the cumulative nature of pressure deviations rather than instantaneous readings alone
2Speed
If reference value is set immediately when engine decelerates, then response speed is fast, but diagnosis accuracy decreases due to pressure lag
Solution Approach 1:
The system applies preliminary action by waiting for a predetermined period after engine deceleration before setting the reference pressure value. This delay allows the pressure system to stabilize and reach equilibrium, ensuring that the reference value reflects the actual steady-state pressure condition rather than transient fluctuations, thereby improving diagnosis accuracy while maintaining reasonable response speed
Solution Approach 2:
The system implements dynamics by adjusting the reference value setting timing based on engine operating conditions. The period setting unit dynamically determines when to set the reference pressure based on the engine deceleration state and pressure stabilization, allowing the system to adapt to varying operating conditions and optimize both response speed and diagnosis accuracy
Data Source
AI summary
An abnormality diagnostic device for an internal combustion engine, comprising: a reference value setting unit that determines a reference value for a pressure in a passage connected to an intake passage of an internal combustion engine; an accumulating unit that acquires a cumulative value by accumulating a difference between the reference value and the pressure from a point in time when the pressure falls below the reference value; and a diagnostic unit that diagnoses an abnormality in the passage based on the cumulative value wherein the reference value setting unit sets the reference value to a pressure after a predetermined period from a time point when the internal combustion decelerates.