Diesel Injector Calibration Sleeve Freeze Protection Insert
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Solution Overview
Problem
The freezing of diesel exhaust fluid (DEF) in injectors for selective catalytic reduction systems causes volume expansion, leading to component shifting and deformation, compromising injector operation and requiring costly external compensation mechanisms.
Innovation Solution
An insert is integrated into the injector, welded to the inlet tube, which absorbs axial forces from freezing DEF and maintains calibration by allowing minimal fluid migration, utilizing elastic modulus compensation and weld connections to prevent calibration sleeve movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If DEF is allowed to migrate freely around injector components, then the injector can operate at lower temperatures without freezing damage, but the calibration precision deteriorates due to component shifting and deformation
Solution Approach 1:
The injector is divided into separate functional components: a calibration sleeve for precision positioning, a freeze protection insert with blocking features to contain frozen DEF, and a solenoid assembly. The insert acts as a barrier that segments the fluid path, preventing frozen DEF from reaching calibration components while allowing liquid DEF to pass through during normal operation.
Solution Approach 2:
The freeze protection insert serves as an intermediary barrier between the frozen DEF and the calibration sleeve. It contains blocking features that prevent direct contact between expanded frozen DEF and precision components, thereby protecting calibration precision while allowing the system to operate in cold temperatures.
2Reliability
If external devices are added to compensate for DEF expansion, then the reliability improves by preventing calibration damage, but the device complexity increases
Solution Approach 1:
The freeze protection functionality is merged with the existing calibration sleeve structure. The insert is integrated into the fluid path and works in conjunction with the calibration sleeve and solenoid assembly, combining calibration and freeze protection functions into a unified design rather than adding separate external compensation devices.
Solution Approach 2:
The calibration sleeve serves multiple functions: it provides precision positioning for the solenoid during calibration and acts as a structural component that works with the freeze protection insert. The insert itself serves dual purposes by both guiding liquid DEF and blocking frozen DEF expansion, reducing the need for additional dedicated components.
3Manufacturing precision
If the calibration sleeve is made more rigid to prevent deformation, then the manufacturing precision improves, but the ease of manufacture deteriorates due to stricter tolerances and higher costs
Solution Approach 1:
The freeze protection insert is installed beforehand to cushion and block the expansion forces of frozen DEF before they can reach the calibration sleeve. This protective barrier allows the calibration sleeve to maintain precise dimensions without requiring excessive rigidity or extremely tight tolerances, as the insert absorbs the expansion stresses.
Solution Approach 2:
The design changes the operational parameters by introducing a blocking mechanism that alters how expansion forces are distributed. Instead of relying solely on the calibration sleeve's rigidity to resist deformation, the system uses the insert to block and redirect expansion forces, allowing for more relaxed manufacturing tolerances on the calibration sleeve while maintaining precision.
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 insert effectively compensates for DEF volume expansion, ensuring consistent injector operation and reducing damage by maintaining calibration and minimizing volume expansion forces, thus preventing operational disruptions and costly component damage.
Implementation Method 1
the elastic modulus of the various injector components
Implementation Method 2
the insert is welded to an inlet tube
Implementation Method 3
DEF freezes at −11° C., which may occur in cold environments when the vehicle is not in use, and the volume of DEF increases by approximately 9% when frozen
Data Source
AI summary
An injector which incorporates the use of an insert to compensate for the change in volume of diesel exhaust fluid as the diesel exhaust fluid freezes, reducing or eliminating the effects on the calibration of the injector. The calibration freeze protection insert is located adjacent a calibration sleeve in the injector, where the insert is welded to an inlet tube. Any axial forces applied to the calibration sleeve from the blocking force of the freezing diesel exhaust fluid are transmitted to the insert, and the position of the insert is maintained by the welds. The insert and the calibration sleeve are configured to only allow small amounts of diesel exhaust fluid to migrate around the injector components, which is able to be compensated for by the elastic modulus of the various injector components.