Secondary Air Flow Estimation Without Dedicated Flow Sensors
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Solution Overview
Problem
Existing secondary air injection systems for internal combustion engines are costly and complex, often relying on flow sensors that are prone to clogging and failure, and there is a need for a more efficient and reliable method to introduce secondary air into the exhaust stream.
Innovation Solution
A method for estimating secondary air flow using standard production sensors and system controls, calculating mass flow through the secondary air injection valve based on intake manifold pressure, temperature, and boost pressure, without relying on flow sensors, and adjusting the control signal accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a flow sensor is used to measure secondary air flow, then measurement precision is improved, but device complexity and reliability worsen due to clogging and failure risks
Solution Approach 1:
The patent removes the flow sensor from the secondary air injection system entirely. Instead of measuring flow directly with a sensor, the system estimates secondary air flow by extracting and utilizing data from existing sensors (manifold absolute pressure sensor, throttle position sensor, engine speed sensor) combined with a flow estimation model, thereby eliminating the unreliable flow sensor while maintaining measurement capability
Solution Approach 2:
The patent introduces a flow estimation model as an intermediary between the existing sensors and the control system. This model processes inputs from MAP sensor, TPS, and engine speed sensor to calculate estimated secondary air flow, serving as a virtual mediator that provides accurate flow measurement without requiring a physical flow sensor in the air path
2Measurement precision
If a flow sensor is installed in the secondary air path, then measurement precision is improved, but device complexity increases due to additional components
Solution Approach 1:
The patent eliminates the flow sensor component from the system, reducing device complexity. The solution extracts and leverages data from already-present sensors (MAP sensor, TPS, engine speed sensor) to achieve flow measurement without adding any new hardware components to the secondary air injection system
Solution Approach 2:
The patent makes the existing sensor suite multi-functional by using the MAP sensor, TPS, and engine speed sensor not only for their primary engine control functions but also for estimating secondary air flow. This universal utilization of existing components achieves flow measurement capability without requiring dedicated flow sensing hardware
3Productivity
If ambient air is pumped into exhaust using a smog pump, then secondary air injection is achieved, but device complexity increases due to additional system components
Solution Approach 1:
The patent removes the smog pump from the system entirely. Instead of actively pumping air, the system extracts and utilizes the naturally pressurized air already present in the intake manifold (charged air from the turbocharger compressor), eliminating the need for additional pumping hardware
Solution Approach 2:
The system makes the intake manifold air serve dual purposes: it continues to supply air for combustion while simultaneously providing the secondary air injection source. The pressurized air from the turbocharger compressor self-services the SAI function without requiring separate pumping equipment
Data Source
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AI summary
Methods and systems using model based and iterative calculations of mass flow throughout an internal combustion engine system. A secondary air injection valve is provided to selectively allow intake air to pass to the exhaust side of the engine system to aid in exothermic reaction with exhaust gasses exiting the engine for various purposes. The iterative calculations of mass flow include estimation of the mass flow through the secondary air injection valve.