Control Valve Arrangement for Fuel Injector Re-pressurization
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Solution Overview
Problem
High pressure fuel injectors face challenges in achieving controlled needle lift speed and rapid closure due to larger inter-valve volumes, which result in steep gain curves for small injections, making them unsuitable for higher inter-valve volumes required for manufacturing simplicity.
Innovation Solution
A control valve arrangement with an additional fluid flow path from the high pressure supply to the inter-valve volume, utilizing a filling valve and control valve system with a guiding section and clearance channels to enhance fluid communication and re-pressurization, allowing for quicker filling and re-pressurization of the inter-valve volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a separate filling valve operated by a hydraulic servo driven by a two-way control valve is used, then the filling valve can have a large flow area and drive the nozzle needle closed quickly, but larger inter-valve volumes take longer to re-pressurise, resulting in steep gain curves for small injections
Solution Approach 1:
The invention divides the control valve into two separate valves: a filling valve with a large flow area for rapid needle closure, and a control valve for precise injection control. This segmentation allows each valve to be optimized for its specific function, resolving the contradiction between fast closure and quick re-pressurization.
Solution Approach 2:
A communication channel is introduced as an intermediary pathway between the first control chamber and the second control chamber. This channel enables rapid re-pressurization of the inter-valve volume by providing a direct fluid communication path, eliminating the time delay that would otherwise occur through the main filling channel alone.
2Ease of manufacture
If larger inter-valve volumes are used to simplify manufacture, then manufacturing is easier, but re-pressurisation takes longer, resulting in steep gain curves for small injections
Solution Approach 1:
By segmenting the control system into two valves with separate functions, the invention allows the inter-valve volume to be enlarged for manufacturing simplicity without compromising injection response. The communication channel compensates for the larger volume by providing a dedicated rapid re-pressurization pathway.
Solution Approach 2:
The communication channel is pre-configured to provide a direct fluid path between control chambers, enabling rapid re-pressurization to occur automatically as soon as the control valve closes, without waiting for the slower main filling channel to replenish the volume.
3Speed
If a three-way valve function is implemented with a separate filling valve, then the filling valve can have a large flow area, but the system becomes more complex
Solution Approach 1:
Instead of making a single valve perform three-way functions, the invention segments the control function into two separate valves. This reduces the complexity of individual valve components while achieving the same overall functionality, as each valve can be simpler in design but work together to provide the required control.
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
This solution enables controlled needle lift and rapid closure, reducing shot-to-shot variations and sensitivity to fuel viscosity, thus avoiding steep gain curves for small injections, even with larger inter-valve volumes, improving manufacturing efficiency.
Implementation Method 1
a filling valve (40) normally biased open by a first spring (46), away from a first seat (26) arranged in the valve housing (22)
Implementation Method 2
a control valve (56) normally biased in a closed position by a second spring (62), in complementary abutment against a second seat (34)
Implementation Method 3
a piston (152) piloting the injection of the fuel into a compression chamber
Implementation Method 4
a filling valve which is operated by a hydraulic servo
Data Source
Figure 1a
Figure 1b~1c
Figure 2a
AI summary
A control valve arrangement (12) of a fuel injector (10) comprises a bore (18) in which a piston (16) is slidably arranged, the piston piloting injection events and the bore opening in direct and unrestricted fluid communication into a first control chamber (24). The arrangement comprises a further fluid communication path from a high pressure line (20) to a second control chamber (68), the further fluid communication path comprising, for example, a clearance, a channel or a bypass orifice.