High-Pressure Accumulator Autofrettage Insert Throttling
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Solution Overview
Problem
Existing high-pressure accumulator designs for injection systems are inefficient in damping pressure waves due to limitations in geometric complexity, tolerance precision, and the need for expensive post-machining operations, particularly with autofrettage processes.
Innovation Solution
A method involving a cylindrical body with fittings and inserts, where the inserts are force-fitted through autofrettage, allowing for precise throttling and complex geometries like stepped bores to optimize pressure wave attenuation, eliminating the need for costly edge rounding and reducing dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional drilled nozzles are used in the rail, then the structure is simple to manufacture, but the damping effectiveness is low and geometric complexity is limited
Solution Approach 1:
The nozzle is separated from the rail body, allowing the nozzle to be manufactured as a separate component with complex internal geometry (stepped bores, curved passages) while the rail maintains its simple forged structure. This segmentation enables each component to be optimized independently for its specific function.
Solution Approach 2:
The separate nozzle acts as an intermediary component that mediates between the high-pressure chamber and the outlet fitting. It provides the complex flow control geometry needed for effective pressure wave damping without requiring the rail itself to have complex internal features.
2Ease of manufacture
If drilled nozzles with simple geometry are used, then manufacturing is easier, but tolerance precision and edge quality are poor requiring expensive post-machining
Solution Approach 1:
By separating the nozzle from the rail, the precision-critical features (edges, bore intersections, throttle geometry) are concentrated in the nozzle component where they can be precisely manufactured through dedicated machining operations, while the rail requires only basic drilling and tapping.
Solution Approach 2:
The nozzle is pre-manufactured with all precision features (stepped bores, curved passages, edge radii, throttle openings) before assembly to the rail. This preliminary fabrication of complex geometry in a separate component avoids the need for expensive post-machining operations on the rail after assembly.
3Ease of operation
If plugged-in nozzles with interference fit are used, then assembly is simple, but they are incompatible with autofrettage processes
Solution Approach 1:
The connection method between nozzle and rail is changed from interference fit (negative clearance) to clearance fit with positive clamping. This parameter change in the dimensional relationship allows the assembly to withstand the high pressures of autofrettage without requiring precise control of negative tolerances, making the process compatible with standard autofrettage operations.
4Reliability
If complex geometric shapes are attempted in drilled nozzles, then damping effectiveness may improve, but manufacturing precision and tolerance control become difficult
Solution Approach 1:
The complex geometry is isolated to the separate nozzle component, which can be manufactured with dedicated precision machining equipment and processes. The rail body remains simple, allowing each component to be manufactured with appropriate precision capabilities for its specific requirements.
Solution Approach 2:
The nozzle can be manufactured using precision copying methods (such as CNC machining from digital models, or even investment casting with precise patterns) to replicate the complex ideal geometry with high fidelity, achieving the desired flow characteristics and pressure wave damping performance.
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 method simplifies manufacturing, achieves precise and effective pressure wave damping with low tolerances, and avoids foreign body introduction, ensuring smooth edges and efficient pressure distribution.
Implementation Method 1
an insert is installed in each chamber, the tightness of the inserts and that of the entry of the fittings is created and the rail assembled in this way is subjected to autofrettage pressure in order to treat the inner surface of the rail and to force fit the inserts into the fitting chamber
Implementation Method 2
A throttle is arranged in the outlet passage in order to attenuate the pressure waves of a downstream injector
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a high-pressure accumulator for a high-pressure injection system made of a cylindrical body (11), which delimits a high-pressure chamber (12, 12a), and connection pieces (13, 13a), which are provided with outlet passages (131, 131a) for a high-pressure liquid, said passages opening into the chamber (12, 12a), and each of which is provided with a throttle in order to weaken pressure waves generated by injectors connected downstream. Each of the connection pieces (13, 13a) has a passage (131, 131a) with a chamber (1312, 1312a) at the outlet, said chamber receiving an insert piece (2, 2a) which is provided with the throttle (22, 22a). The insert piece (2, 2a) is fixed in the chamber (1312, 1312a) in a force-fitting manner by an autofrettage process of the high-pressure accumulator.