Low Pressure EGR Apparatus Failure Mode Detection
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Solution Overview
Problem
Existing low pressure exhaust gas recirculation (EGR) systems face challenges in efficiently recirculating a large quantity of EGR gas due to the low exhaust gas pressure and intake air negative pressure, leading to increased size and complexity of the apparatus, and difficulties in determining failures in the intake air throttle valve.
Innovation Solution
A low pressure EGR apparatus with a supercharger, incorporating a low pressure EGR passage, a low pressure EGR valve, a valve drive device, a throttle valve, a synchronizing mechanism, a failure mode setting mechanism, and a failure mode determining device, which includes a spring, a throttle valve side stopper, and an EGR valve side stopper, to manage the flow quantity and determine failure modes based on rotational positions, reducing the operational angular range and apparatus size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the opening degree of the intake air throttle valve is increased to recirculate more EGR gas, then the quantity of recirculated EGR gas increases, but the intake air negative pressure decreases reducing recirculation efficiency
Solution Approach 1:
The patent dynamically adjusts the opening degree of the intake air throttle valve based on the operational state of the low pressure EGR valve. When the low pressure EGR valve opens fully, the throttle valve closes to maximize negative pressure and recirculation efficiency. This dynamic coordination allows the system to recirculate large quantities of EGR gas while maintaining high recirculation efficiency through optimized pressure differential management.
2Reliability
If the operational angular range of the cam plate is increased to accommodate link device failures, then the reliability improves, but the size of the EGR apparatus increases
Solution Approach 1:
The patent incorporates stoppers that preliminarily limit the rotational range of the cam plate before failure conditions occur. These stoppers prevent excessive rotation beyond the normal operational range, thereby maintaining a compact apparatus size while still providing sufficient protection against link device failures. The stoppers act as preventive measures that constrain motion within safe boundaries.
Solution Approach 2:
The stoppers serve as intermediary elements between the cam plate and the valve mechanism. They mediate the rotational motion by providing mechanical constraints that prevent the cam plate from rotating beyond its normal operational range. This intermediary constraint system enables failure protection without requiring an increased operational angular range, thus maintaining compact apparatus dimensions.
3Measurement precision
If a dedicated actuator is added to drive the intake air throttle valve, then the control precision improves, but the device complexity increases
Solution Approach 1:
The patent employs a single actuator that performs multiple functions: it drives both the low pressure EGR valve and the intake air throttle valve through the cam plate mechanism. This multi-functional actuator eliminates the need for a dedicated actuator for the throttle valve, thereby reducing device complexity while maintaining precise control through the synchronized cam plate mechanism that coordinates both valve operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient recirculation of a large quantity of EGR gas while maintaining engine performance and reducing the size of the EGR apparatus by determining failure modes within the normal operational range, thus preventing unnecessary size increases and maintaining intake air flow.
Implementation Method 1
a spring, a throttle valve side stopper and an EGR valve side stopper. The spring urges the throttle valve in an urging direction, which is opposite from the closing direction of the throttle valve
Implementation Method 2
a supercharger installed in an intake and exhaust system that includes an intake passage, which conducts intake air to be supplied to the internal combustion engine and has a compressor of the supercharger
Data Source
AI summary
When a failure occurs in synchronizing mechanism, an intake air throttle valve is rotated in a direction that is opposite from a normal operational time valve closing direction, so that an arm of a driven plate contacts a throttle valve side stopper to stop rotation of the intake air throttle valve. Thereafter, when a low pressure EGR valve is rotated from a full close position to a full open position, an EGR valve side stopper contacts the arm of the driven plate to stop the low pressure EGR valve. A rotational angle of the EGR valve is sensed with a sensor and is outputted to an ECU. The ECU determines that a failure mode is set when a valve angle sensed with the sensor coincides with a rotation stop position of the EGR valve.