Air Driven Hydraulic Pump Reductant Dosing Control
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Solution Overview
Problem
Current reductant dosing systems for internal combustion engines face challenges in achieving precise dosing rates insensitive to pressure variations, requiring complex motor control systems, continuous air supply, and additional heating means to prevent residue freezing, especially in lean combustion engines where NOx reduction is necessary.
Innovation Solution
An air-driven hydraulic pump system with a pressure sensor and dosing control unit that uses solenoid valves to control pressure and a two-stage PWM controller to maintain consistent reductant pressure, allowing for accurate dosing without continuous air flow and reducing the need for additional heating, utilizing compressed air from the engine turbo.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a motor-driven pump is used to maintain rail pressure, then pressure control precision is improved, but device complexity increases due to motor control requirements
Solution Approach 1:
The patent replaces the motor-driven pump with a pneumatic pump that uses compressed air to generate hydraulic pressure. This substitution eliminates the need for complex motor control systems while maintaining the ability to control rail pressure through pneumatic actuation of the pump mechanism.
Solution Approach 2:
The patent employs a pneumatic pump that converts pneumatic energy from compressed air into hydraulic pressure in the reductant rail. This pneumatic-hydraulic conversion system achieves pressure control without requiring electrical motors or complex electronic control systems.
2Measurement precision
If a metering pump with continuous air supply is used, then dosing precision is improved, but device complexity increases due to air supply requirements
Solution Approach 1:
The patent utilizes the engine's existing turbocharger compressed air output for multiple purposes: both for engine operation and for driving the reductant pump. This multi-functional use of the turbocharger's compressed air eliminates the need for a separate air supply system.
Solution Approach 2:
The system uses the engine's own turbocharger to provide compressed air for the reductant dosing system, making the system self-sufficient without requiring external air supply infrastructure.
3Device complexity
If reductant residue is left in the dosing system, then system simplicity is maintained, but harmful factors increase due to freezing risk
Solution Approach 1:
The patent implements a purge function that extracts and removes reductant residue from the dosing system components using compressed air. This extraction of residue eliminates the freezing hazard while maintaining system simplicity by using the existing pneumatic infrastructure.
Solution Approach 2:
The system performs preliminary purging of reductant residue before shutdown or cold conditions occur, preventing freezing issues before they arise. This proactive approach maintains system simplicity while eliminating the harmful freezing effect.
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
The system achieves precise and consistent reductant dosing rates, reduces system complexity, eliminates the need for continuous air supply, and simplifies heating requirements, enabling efficient NOx reduction in lean combustion engines.
Implementation Method 1
an air driven hydraulic pump with an inlet port fluidly coupled to a compressed air source
Implementation Method 2
a hydraulic buffer fluidly connected to an injector for reductant dosing
Implementation Method 3
a pressure sensor positioned in a hydraulic buffer to measure the pressure of reductant supplied by an air driven hydraulic pump
Implementation Method 4
The strokes and the pressure in the air driven hydraulic pump are controlled by a DCU through operating the solenoid valves to feed and release air
Implementation Method 5
The reductant dosing rate is controlled with a PWM controller, which generates a PWM signal to drive the injector
Implementation Method 6
After dosing, the shut-off valve opens. The reductant residue in the air driven hydraulic pump and the hydraulic buffer is drained under pressure in the pump
Data Source
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AI summary
A dosing system for delivering reductant to an exhaust gas treatment system of an internal combustion engine using air driven hydraulic pumps for closed-loop controlling reductant pressure and a two-stage PWM control method for controlling dosing rate. Reductant residue in the dosing systems is purged by using compressed air after a dosing process completes, and when the air driven hydraulic pumps are positioned inside a reductant tank, dedicated heating means for the pumps is not necessary. The air driven hydraulic pumps can also use low pressure compressed air, and the closed-loop pressure control together with the two-stage PWM control allow dosing accuracy insensitive to pressure variations in compressed air. These features enable the dosing system use a variety of compressed air sources, including an engine turbo.